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UC-NRLF 


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ondensers 


From 

Power 


/. 


s 


LIBRARY 
HKiymSJJY  OF  CALIFORNIA 

PaVis 


CONDENSERS. 


A  series  of  Lectures  and  Articles  upon   the  Subject 
reprinted  from  the  columns  of 


NEW    YORK: 

The  Power  Publishing  Company, 

World  Building. 

1901. 


LIBRARY 

UNIVERSITY  OF  CALIFORNIA 

DAVIS 


Entered  accotding  to  act  of  Congress,  in  the  year  1900,  by  The  Power  Publishing 
Company,  in  the  office  of  the  Librarian  of  Congress  at  Washington. 


LECTURE  VIII.— CONDENSERS. 

BY    F.   R.   LOW. 


If  you  build  up  a  solid  column  of  bricks  the  pressure  which  it 
exerts  on  its  base  will  increase  directly  as  the  height  of  the  col- 
umn. A  column  ten  feet  in  height  will  press  twice  as  hard  on 
its  base  as  a  column  five  feet  high,  and  a  column  ioo  feet  high 
ten  times  as  hard  as  a  io-foot  column. 

Now,  the  point  I  want  to  make  is  that  the  pressure  per  square 
inch  of  base  depends  altogether  on  the  height  and  not  on  the 
width  or  diameter  of  the  column.  A  column  2  feet  square  will, 
it  is  true,  press  on  its  base  with  four  times  the  pressure  of  a  col- 
umn one  foot  square  and  of  the  same  height,  because  there  are 
four  times  as  many  bricks  in  it  and  it  weighs  four  times  as  much, 
but  there  is  also  four  times  as  much  base  to  it,  so  that  the  pres- 
sure per  square  inch  of  base  is  entirely  independent  of  the  cross 
section  and  depends  upon  the  height  alone. 

The  same  thing  is  true  of  water.  A  cubic  foot  of  fresh  water 
weighs  62.355  pounds  at  62  degrees  Fahrenheit.  It  is  easy  to 
remember  this  weight  approximately,  for  it  is  the  same  as  the  de- 
grees and  62  is  a  standard  temperature  in  dealing  with  water.  A 
cubic  foot  rests  on  a  base  of  144  square  inches  and  is  a  foot  high, 
so  that  the  pressure  per  square  inch  on  the  base  would  be 

62.355  ~r-T44  —  °-433  of  a  pound 
and  for  every  foot  in  height  that  we  build  our  column  or  fill  our 
pipe  with  water  we  gain  0.433  °f  a  pound  pressure  per  square 
inch.     If  one  foot  or  12  inches  gives  us  0.433  of  a  pound  it  would 
take  a  column 

12  -—  .433  =  27.71  inches 
in  height  to  exert  a  pressure  of- one  pound  per  square  inch.     For 


Fluid  Pressure  is  Dependent  upon  Height  of  Column. 


every  27.71  inches  in  vertical  height  between  the  point  at  which 
you  are  measuring  and  the  top  of  a  column  of  still  water  there  wilt 
be  a  pressure  of  a  pound  to  the  square  inch,  and  it  makes  no  dif- 
ference whether  you  are  measuring  the  pressure  at  the  bottom  of 
a  one- eighth  inch  pipe,  a  twenty  foot  stand-pipe,  or  a  lake,  or  the 
ocean  itself.  Every  once  in  a  while  we  have  to  explain  this  to- 
the  man  who  believes  it  takes  more  power  to  feed  into  the  bot- 
tom of  a  tank  than  into  the  top,  on  account  of  the  weight  of 
water  in  the  tank.  The  bottom  of  the  tank  holds  up  all  the 
water  except  the  column  directly  over  the  opening  of  the  deliv- 
ery pipe,  so  that  the  additional  pressure  on  the  pump  is  due  only 
to  the  depth  of  water  in  the  tank,  not  to  the  size  of  the  body, 
and  it  is  impossible  to  feed  into  the  top  without  increasing  the 
height  of  the  column  fully  as  much.  It  makes  no  difference 
whether  the  height  is  due 
to  the  depth  of  the  water 
inside  the  tank  or  an  ad- 
ditional length  of  pipe 
outside.  The  difference 
between  the  water  and 
the  column  of  bricks  is 
that  while  the  pressure 
of  the  latter  can  act  only 
vertically  that  of  the 
water  can  act  in  all  di- 
rections so  that  as  you 

lower  a  body  into  the  water  the  pressure  upon  its  surface  in  all 
directions  increases  one  pound  per  square  inch  for  every  27.71 
inches  of  depth  of  water  above  it.  In  Fig.  1,  for  instance,  the 
pressure  due  to  the  column  of  water  P  will  act  upward  upon  the 
piston  A  and  sidewise  upon  the  pistons  B  and  G  as  well  as  down- 
ward upon  the  piston  D. 

We  live  at  the  bottom  of  an  ocean  of  air.  The  winds  are  its 
currents,  we  can  heat  it,  cool  it,  breathe  and  handle  it,  weigh  it, 
and  pump  it  as  we  would  water.  The  depth  of  this  atmospheric 
ocean  cannot  be  determined  as  positively  as  could  one  of  liquid, 
for  the  air  is  elastic  and  expands  as  the  pressure  decreases  in  the 
upper  layers.  It  is  variously  estimated  at  from  30  to  212  miles. 
We  can,  however,  determine  very  simply  how  much  pressure  it 
exerts  per  square  inch. 


^1 

r 

P 

/ 

1 

: 

=fe= 

;- 

z^^s. 

B 

; — ; ' p 

—~^== = 

Fi 

9- 

EfT^ 

Measuring  the  Pressure  of  the  Atmosphere. 


Here  is  a  U-tube,  Fig.  2,  into  which  a  quantity  of  mercury 
"has  been  poured.  It  stands  at  an  equal  height  in  both  legs.  Into 
one  leg  I  pour  some  water  on  top  of  the  mercury,  and  the  mer- 
cury is  depressed  in  that  leg,  and  rises  in  the  other.  ^ 
The  difference  in  level  of  the  mercury  is  a  meas- 
ure of  the  weight  or  downward  pressure  of  the 
water. 

The  mercury  below  the  line  A  B  balances  in 
lx>th  legs  and  the  mass  of  mercury  above  that 
line  in  the  right  leg  just  balances  the  weight  or 
pressure  of  the  water  in  the  other.  The  pressure 
of  the  atmosphere  makes  no  difference  in  this  ex- 
periment, for  it  is  exerted  on  both  columns  equal- 
ly. Now  we  can  find  the  pressure  of  the  atmos-  Fig.  2. 
phere  in  a  similar  way  by  making  it  act  on  one 
end  of  the  mercury  column  as  does  the  water  here  and  keeping  it 
away  from  the  other. 

Here  is  a  glass  tube  about  a  yard  in  length  and  filled  with  mer- 
cury. Closing  one  end 
with  my  thumb  to  pre- 
vent a  premature  escape, 
I  invert  it  in  a  bowl  of 
mercury  as  in  Fig.  3. 
This  is  handier  than  the 
U-tube  but  the  principle 
is  the  same.  The  bowl 
is  in  effect  the  other  leg 
of  the  tube  and  no  mat- 
ter what  its  size  may  be 
the  atmosphere  exerts  a 
certain  pressure  on  each 
square  inch  of  its  surface, 
except  at  the  point 
covered  by  the  tube, 
and  here  the  mercury 
rises  until  it  forms  a 
column  high  enough  to 
exert  the  same  pressure 
per  square  inch,  so   that  the  height  of  the  column  is  a  measure 


4  Nature  and  Measurement  of  a    Vacuum. 

of  the  atmospheric  pressure.  This  column  will  be  approximate- 
ly 30  inches,  and  as  a  cubic  inch  of  mercury  weighs  about  a 
half  a  pound,  each  two  inches  of  height  will  be  equal  to  a  pound 
pressure,  so  that  the  pressure  exerted  by  the  atmosphere  is  about 
1 5  pounds  per  square  inch.  This  pressure  depends  first  upon  the 
nature  of  the  atmosphere.  You  know  that  steam  or  aqueous 
vapor  is  lighter  than  air  at  the  same  pressure,  so  the  more  moist- 
ure there  is  in  the  air  the  lighter  the  column  of  atmosphere 
above  us,  and  the  less  the  height  to  which  our  column  of  mer- 
cury will  rise  to  balance  it.  Also  the  warmer  the  air  becomes 
the  lighter  it  is.  Again,  if  we  carry  our  apparatus  to  the  top 
of  a  high  mountain  we  shall  find  a  considerable  difference  in  the 
height  of  the  column,  because  we  have  lessened  the  height  of 
the  column  of  air  above  us.  This  arrangement,  which  is 
known  as  a  "barometer,"  is  therefore  of  use  in  indicating  coming 
changes  in  the  weather,  and  elevations  above  the  sea  level,  at 
which  our  experiment  is  supposed  to  have  been  made. 

We  are  then  subjected  all  the  time  to  a  pressure  of  15  pounds 
to  the  square  inch  all  over  our  bodies,  yet  we  suffer  no  inconven- 
ience, in  fact,  it  took  mankind  a  long  while  to  find  it  out,  be- 
cause the  pressure  is  the  same  in  all  directions,  it  is  exerted  in- 
side as  well  as  out,  and  there  is  no  unbalanced  pressure.  It  is 
only  when  the  atmospheric  pressure  is  removed  from  one  side  and 
allowed  to  act  upon  another  that  we  get  any  effect.  In  a  space 
from  which  the  air  has  been  removed  without  allowing  anything 
else  to  enter,  a  "vacuum"  is  said  to  exist,  and  the  vacuum  is 
more  or  less  complete  according  to  the  more  or  less  complete  re- 
moval of  the  air.  In  the  space  A  in  Fig.  3,  exists  the  most  per- 
fect vacuum  we  are  able  to  create,  for  the  mercury  in  receding 
has  left  nothing  behind  it,  except  possibly  a  little  mercurial  va- 
por if  there  have  been  no  air  bubbles  and  no  moisture  between 
the  mercury  and  the  glass.  With  this  complete  vacuum  above  it 
the  mercury  will  rise  about  30  inches,  and  we  would  say  that  we 
had  "30  inches  of  vacuum."  What  we  mean  is  that  the  pressure 
has  been  so  completely  removed  from  the  space  A  that  the  at- 
mospheric pressure  is  able  to  support  30  inches  of  mercury 
against  the  pressure  that  is  left.  Suppose  we  let  a  little  air  into 
A.  The  mercury  would  fall  more  or  less  according  to  the  amount 
of  air  admitted,  because  this  air  would  exert  some  pressure,  there 


Nature  and  Measurement  of  a    Vacuum.  5 

would  be  less  difference  between  the  pressure  in  A  and  that  of 
the  atmosphere,  and  the  atmosphere  would  be  able  to  support  a 
lesser  column  against  this  greater  pressure.  If  the  column  now 
was  18  inches  high  we  would  say  that  we  had  18  inches  of  vac- 
uum, and  should  mean  that  the  atmospheric  pressure  could  sup- 
port 18  inches  oi  mercury  against  the  pressure  in  our  vacuum. 
These  are  the  "inches"  of  vacuum  upon  the  ordinary  vacuum 
gage.  When  the  pointer  stands  at  26  inches  it  means  that  there 
is  difference  enough  between  the  pressure  in  the  condenser  and 
that  of  the  atmosphere  to  support  a  column  of  mercury  26  inches 
high.  If  with  an  absolute  vacuum  the  barometer  stood  at  30 
inches,  and  if  a  cubic  inch  of  mercury  weighed  half  a  pound  the 
atmospheric  pressure  would  be  15  pounds,  and  two  inches  would 
equal  one  pound.  As  a  matter  of  fact  the  height  of  the  barome- 
ter varies  and  mercury  weighs  only  .49  of  a  pound  to  the  cubic 
inch,  so  that  the  atmospheric  pressure  is  nearer  14.7  than  15 
pounds.  When  you  put  your  hand  over  an  opening  into  a  space 
containing  a  vacuum  you  feel  it  drawn  to  and  held  down  very 
hard  upon  the  opening.  This  is  due  not  to  any  attractive  power 
of  the  vacuum,  but  to  the  pressure  of  the  atmosphere  upon  the 
back  of  your  hand  unbalanced  by  an  equal  pressure  on  the  area 
in  contact  with  the  opening  to  the  vacuum. 

Here  is  an  implement  which  every  schoolboy  knows  under  the 
name  of  a  "sucker,"  a  circular  pad  of  leather,  thick,  but  pliable, 
with  a  string  through  its  center.  It  has  been  soaking  in  water. 
I  press  it  against  the  smooth  wooden  seat  of  this  chair  and  am 
able,  you  see,  to  lift  the  chair  with  a  string.  The  boys  used  to 
get  themselves  into  disrepute  with  the  householders  in  the  vicin- 
ity of  the  school  by  pulling  the  bricks  out  of  the  sidewalk  in  this 
way.  This  action  is  not  due  to  any  attractive  or  adhesive  prop- 
erty of  the  leather,  but  to  the  fact  that  there  is  a  pressure  of 
about  15  pounds  per  square  inch  pushing  the  leather  against  the 
chair,  and  the  atmosphere  owing  to  the  more  or  less  complete 
contact  of  the  wet  leather  with  the  surface  on  which  it  rests  can- 
not get  to  the  under  surface  to  balance  it.  The  disk  is  four 
inches  in  diameter,  having  an  area  of  12.5  square  inches,  and  the 
atmosphere  exerts  a  pressure  on  its  surface  of  14.7  X  I2- 5  = 
183.75  pounds  with  which  the  "sucker"  would  resist  separation 
from   the  surface  to  which  it  was  attached,  if  the  pressure  was 


How   Water  is  Lifted  by  Means  of  a    Vacuum. 


entirely  removed  from  its   under-side,  and  other  surface,  and  the 
leather  perfectly  air  tight. 

We  are  accustomed  to  say  that  water  is  '  'sucked  up' '  or  '  'drawn 
up"  by  a  pump  as  though  there  was  some  pulling  property  to  the 
vacuum  which  it  creates,  when  as  a  fact  the  water  is  pushed  up 
by  the  atmospheric  pres- 
sure acting  on  the  sur- 
face of  the  water  in  the 
well.  If  in  Fig.  3,  we 
had  a  tube  of  water  in- 
stead o  f  mercury  w  e 
should  find  that  the 
water  would  rise  in  it 
about  34  feet  instead  of 
30  inches.  We  have 
seen  that  it  takes  a  col- 
umn of  water  27  71  in- 
ches high  to  exert  a 
pressure  of  one  pound, 
then  the  atmospheric 
pressure  of  14.7  pounds 
could  support  a  column 
of 

2771  X  r4.7=33  94  ft 
12 

In  Fig.  4,  we  have  a 
steam  pump  drawing 
water  from  a  well. 
Steam  acting  on  the  pis- 
ton A  pushes  the  piston 
B  toward  the  left,  forcing 
the  water  before  it 
through  the  upper  valve 
to  the  discharge  pipe  and  leaving  behind  it  a  more  or  less  complete 
vacuum  in  the  space  C.  Connected  to  the  space  C  through  the 
lower  valves  is  the  pipe  P,  the  lower  end  of  which  is  immersed  in 
the  water  of  the  well.  Here  we  have  a  reproduction  (Fig.  4)  of 
Fig.  3.  The  well  is  the  bowl,  the  pipe  P  is  the  glass  tube,  the 
vacuous  space  C  corresponds  with  the  vacuous  space  A.     There 


Limitations  of  Lift. 


is  this  difference,  however,  the  pipe  P  is  not  so  long  but  that  the 
atmospheric  pressure  can  force  the  water  clear  through  it,  through 
the  valve  into  the  cylinder  C,  ready  to  be  forced  out  again  when 
the  piston  moves  in  the  other  direction.  The  difference  in  pres- 
sure between  the  cylinder  and  the  atmosphere  must  be  sufficient 
to  lift  the  water  from  the  level  in  the  well  to  the  level  of  the 
pump  cylinder,  to  lift  the  valve  and  to  induce  a  flow  sufficiently 
to  keep  the  cylinder  full  behind  the  receding  piston,  and  these 
considerations  limit  the  distance  that  we  can  place  a  pump  above 
its  source  of  supply,  in  other  words  its  "lift."  In  the  first  place 
we  cannot  get  a  perfect  vacuum  in  contact  with  water.  You  re- 
member that  the  boiling  point  of  water  de- 
pends upon  the  pressure.  In  a  boiler  with 
a  pressure  of  60  pounds  by  the  gage,  the 
water  will  not  boil  until  it  is  over  3000. 
Under  the  pressure  of  the  atmosphere  it 
boils  at  2120,  and  as  you  reduce  the  pres- 
sure below  that  of  the  atmosphere  the  boil- 
3  ing  point  lowers  rapidly.  You  can  even  boil 
water  at  32  °  if  you  reduce  the  pressure 
power.y.r.  sufficiently.     In  the  table    on  page   8   are 

Fl£-  5-  shown  the  relations  of  pressure  and  tempera- 

ture for  water  at  from  32 °  to  2120.  This  means  that  if  we  had 
an  arrangement  like  Fig.  5,  starting  with  a  complete  vacuum  in 
chamber  A  the  mercury  in  the  tube  would  not  rise  above  the  level 
in  the  cup  because  there  is  a  complete  vacuum  both  in  A  and  B. 
Now  if  water  of  32  °  be  introduced  into  A  it  would  boil  and  give  off 
vapor  until  the  pressure  in  A  arose  to  .089  of  a  pound,  and  the 
mercury  would  rise  in  B  181  thousandths  of  an  inch.  A  complete 
vacuum  as  given  by  this  table  is  14.7  pounds,  or  29.922  inches, 
but  the  introduction  of  the  water  even  at  32  °  has  reduced  the 
vacuum  to  29.922 — .181=29.741  inches.  The  heat  necessary  to 
convert  the  water  into  vapor,  which  you  will  remember  from  an 
earlier  lecture  was  considerable  in  amount  and  was  called  the  latent 
heat,  coming  from  the  water  and  its  surroundings,  the  water  would 
be  frozen,  and  I  have  seen  ice  made  by  simply  spraying  water  into 
a  space  in  which  a  high  degree  of  vacuum  was  maintained.  If 
the  water  was  6o°  the  vacuum  would  be  impaired  .571  of  an  inch 
or  .  254  of  a  pound.     This  is  the  reason  it  is  so  difficult  to  pump  hot 


Temperature  of  Steam  Below  Atmospheric  Pressure. 


water.  If  the  water  in  Fig  4  was  1500  the  space  Cleft  by  the 
piston,  instead  of  being  a  nearly  complete  vacuum,  would  be  filled 
with  steam  of  3. 708  pounds  pressure,  leaving  only  14. 700 — 3. 708= 


Pressure. 

Vacuum. 

Temperature 

Inches  of 

Lbs.  per 

Inches  of 

Lbs.  per 

mercury. 

square  inch. 

mercury. 

square  inch 

Fahrenheit. 

Inches. 

• 

32° 

.181 

.089 

29  741 

14.611 

35° 

.204 

.100 

29  718 

14  600 

40° 

.248 

.122 

29  674 

14.578 

45° 

.299 

.147 

29.623 

14.553 

50° 

.362 

.178 

29.560 

14  522 

55° 

.426 

.214 

29.496 

14.486 

60° 

.517 

.254 

29.405 

14  446 

65° 

.619 

.304 

29  303 

14.396 

70° 

.733 

.360 

29,189 

14  340 

75° 

.869 

.427 

29.053 

14.273 

80° 

1024 

.503 

28.898 

14  197 

85° 

1205 

.592 

28  717 

14  108 

90° 

1.4L0 

.693 

28.512 

14  007 

95° 

1.647 

.809 

28.275 

13.891 

100° 

1917 

.942 

28.005 

13.758 

105° 

2.229 

1.095 

27.693 

13  605 

110° 

2  579 

1.267 

27  343 

13  433 

115° 

2  976 

1.462 

26  846 

13.238 

120° 

3.430 

1685 

26  492 

13,015 

125° 

3.933 

1932 

25  989 

12.768 

130° 

4  509 

2  215 

25.413 

12.485 

135° 

5.174 

2  542 

24.748 

12.158 

140° 

5.860 

2  879 

24.062 

11.821 

145° 

6  662 

3  273 

23.262 

11.427 

150° 

7  548 

3  708 

22.374 

10  992 

155° 

8.535 

4  193 

21.387 

10  507 

160° 

9.630 

4.731 

20.292 

9.969 

165° 

10  843 

5  327 

19.079 

9.373 

•170° 

12.183 

5  985 

17.739 

8  715 

175° 

13.654 

6  708 

16.268 

7  992 

180° 

15.291 

7  511 

14.631 

7  189 

185° 

17.044 

8.375 

12.878 

6  325 

190° 

19  001 

9  335 

10.921 

5  365 

195° 

21139 

10  385 

8  783 

4  315 

200° 

23.461 

11526 

6.461 

3  17,4 

205° 

25.994 

12  770 

3.928 

1930 

2'0° 

28.753 

14  126 

1.169 

.574 

212° 

29.922 

14  700 

0.000 

0.000 

10.992  pounds  to  raise  the  water  and  force  it  into  the  pump.  If 
the  water  was  2120  it  would  give  off  steam  equal  in  pressure  to 
that  of  the  atmosphere,  and  we  have  no  available  force  at  all. 


Absolute  Pressure.  9 

These  relations  between  pressure  and  temperature  are  simply 
those  for  aqueous  vapor  or  steam.  When  air  is  present  the  pres- 
sure will  be  higher  for  a  given  temperature.  For  this  reason  the 
vacuum  or  pressure  in  a  condenser  is  not  that  due  to  the  temper- 
ature of  its  contents  as  given  in  a  table  of  the  physical  properties 
of  steam  for  it  is  not  steam  alone  with  which  we  are  dealing  but 
a  mixture  of  steam  and  air. 

You  are  now  in  a  position  to  appreciate  what  is  meant  by  '  'ab- 
solute" pressure.  It  is  the  pressure  reckoned  from  a  complete 
vacuum  as  are  the  pressures  in  the  above  table,  and  atmospheric 
pressure  which  is  the  zero  of  the  ordinary  steam  gage  and  of  what 


Fig.  6. 

is  referred  to  as  "gage  pressure"  is  about  14.7  pounds  absolute, 
varying  with  the  barometer.  In  order  to  get  the  "absolute" 
pressure  then  we  must  add  the  barometer's  pressure,  14.7  pounds, 
or  15  if  we  do  not  care  to  be  very  precise,  to  the  pressure  indi- 
cated by  the  gage.  The  steam  tables  are  given  in  absolute 
pressures,  and  we  have  to  take  the  absolute,  not  gage  pressure, 
when  laying  out  the  expansion  line,  or  figuring  problems  in 
which  expansion  is  involved. 

There  is  this  difference  between  pumping  air  and  water,  that 


io  Pumping  Air. 

water  is  either  there  or  not  there;  there  is  no  half  way  about  it. 
It  is  neither  expansible  nor  compressible  by  change  of  pressure, 
and  it  may  be  handled  in  mass.  In  Fig.  6,  for  instance,  we  have 
a  closed  vessel  of  water  at  A  and  another  of  air  at  B.  Now  when 
the  pump  connected  with  A  is  operated  a  volume  of,  say  one- 
fifth,  of  the  water  is  removed,  the  water  left  in  the  tank  falls, 
there  is  nothing  to  take  its  place,  and  a  practically  complete  vac- 
uum is  left  behind.  But  in  the  case  of  the  air,  when  one-fifth  of 
the  volume  is  removed  by  a  stroke  of  the  pump,  the  remainder, 
instead  of  assuming  a  level  and  leaving  a  vacuum  at  the  top  as 
the  water  did,  expands  and  fills  the  whole  space.  Before  the 
pump  was  operated  the  air  was  at  atmospheric  pressure,  say  15 
pounds  to  the  square  inch  absolute.  The  operation  of  the  pump 
removes  one-fifth  of  its  volume,  and  the  remaining  four-fifths  ex- 
pands to  fill  the  complete  volume.  In  this  expansion,  its  pres- 
sure would  be  reduced  to  four-fifths  of  the  former  pressure,  equal 
to  1 2  pounds,  so  that  instead  of  having  at  once  a  complete  vac- 
uum in  the  chamber  as  with  the  water,  we  have  only  reduced  the 
pressure  three  pounds  below  the  atmospheric  pressure  outside, 
and  if  a  column  of  mercury  be  connected  with  the  chamber,  as 
shown  at  B,  we  shall  find  that  in  the  case  of  the  air  it  will  only 
stand  about  6  inches  in  height,  for  the  sustaining  force  is  the  dif- 
ference between  the  inside  and  outside  of  the  chamber,  which  is 
15  —  12=3  pounds,  and  as  one  inch  in  height  exerts  a  pressure 
of  one-half  pound  per  square  inch  on  its  base,  3  pounds  would 
balance  3-^.5  =  6  inches  in  height.  In  this  case  there  is  said 
to  be  6  inches  or  3  pounds  of  vacuum  in  the  vessel. 

By  further  reducing  the  air  in  the  vessel,  we  can  produce  great- 
er differences  in  pressure  between  the  inside  and  outside  and  the 
atmosphere  will  press  the  harder  toward  the  inside  of  the  vessel, 
its  pressure  being  measured  in  the  inches  of  mercury  which  it 
will  lift,  or  the  pressure  per  square  inch  which  it  exerts.  All 
questions  in  regard  to  a  vacuum  become  plain  when  we  consider 
that  the  atmosphere  itself  exerts  a  pressure  of  nearly  15  pounds, 
and  measure  everything  from  an  absolute  zero  15  pounds  below 
the  atmospheric  pressure. 

When  an  engine  is  run  without  a  condenser  the  steam  with 
which  the  cylinder  is  filled  at  the  end  of  the  stroke  has  to  be 


Production  of  Vacuum  bv  Condensation. 


1 1 


forced  out  against  the  pressure  of  the  atmosphere,  about  15 
pounds  to  the  square  inch.  It  is  possible  from  the  nature  of 
steam  to  remove  the  atmospheric  pressure  with,  in  most  cases,  a 
decided  gain.  One  pound  of  steam  at  atmospheric  pressure  oc- 
cupies 1 ,642  times  as  much  room  as  it  does  in  the  state  of  water. 
If  therefore  when  the  stroke  has  been  completed  and  we  are 
ready  for  the  piston  to  come  back  we  inject  a  little  cold  water 
into  the  spent  steam,  it  will  condense   to  about  one  1600th  of 


Fie\  7. 

its  volume,  and  leave  a  vacuum  into  which  the  piston  can  return 
without  having  to  force  back  the  atmosphere.  This  is  the  way 
the  earlier  engines  were  run,  the  condensation  taking  place  in  the 
cylinder  itself,  and,  moreover,  the  vacuum  was  all  that  made  the 
engine  operative,  for  the  steam  carried  was  bul  little  above  atmos- 
pheric pressure.  Watt's  introduction  of  the  separate  condenser 
was  his  greatest  contribution  to  the  steam  engine,  and  constituted 


12 


Gain  by  Condeiisation . 


his  most  important  invention,  for  he  was  not  as  you  know  the  in- 
ventor of  the  engine,  but  its  improver.  The  operation  of  the 
condenser  is  shown  in  Fig.  7.  The  denser  steam  in  the  stuffing 
box  end  of  the  cylinder  is  pushing  the  piston  to  the  left,  forcing 
the  spent  steam  of  the  previous  stroke  to  the  condenser  where, 
instead  of  having  to  be  forced  out  against  1 5  pounds  pressure  of 
the  atmosphere,  it  is  condensed  by  coming  into  contact  with  a 
spray  of  cold  water.  The  condensed  water,  the  water  of  injec- 
tion and  the  air  which  has  entered  with  the  steam  and  by  leak- 
age are  drawn  out  by  an  "air  pump,"  and  the  comparatively 
small  volume  which  it  has  to  expel  against  the  atmospheric  pres- 
sure, leaves  a  large  margin  a    95  lbs,  b     c 

.  ,         -  °  I    ABSOLUTE  ' 

of  power  gained  after  that 
required  to  run  the  pump 
is  deducted. 

L,et  us  first  consider  the 
nature  and  extent  of  the 
saving  due  to  a  condenser, 
and  when  it  is  and  is  not 
advisable  to  use  it. 

Suppose  we  have  an  en- 
gine with  an  initial  pres- 
sure of  80  pounds  gage,= 
95  pounds  absolute,  cutting 
off  at  one-third.  The 
mean  effective  pressure,  if  the  engine  ran  non-condensing  and 
made  the  perfect  diagram  represented  by  the  full  lines  in  Fig.  8, 
would  be  51.25  pounds.  If  we  put  on  a  condenser  and  reduce 
the  back  pressure  from  that  of  the  atmosphere,  say  15  pounds  ab- 
solute, to  3  pounds  absolute,  the  diagram,  to  give  the  same  mean 
effective  pressure  representing  the  same  load  on  the  engine,  would 
take  the  form  shown  by  the  dotted  lines.    • 

In  the  non- condensing  diagram,  the  boiler  has  to  fill  the  cylin- 
der up  to  the  point  C,  and  the  volume  of  steam  at  cut-off  is  pro- 
portional to  the  line  A  C.  In  the  condensing  engine  the  steam 
is  cut  off  at  B,  and  the  steam  is  proportional  to  the  line  A  B. 
Now  A  C  is  .33^3  of  the  volume  of  the  cylinder  and  A  B  is  only 
.23256,  so  we  have  apparently  saved 


Fig,   8. 


53  LBS. ABSOLUTE 


Gain  by  Condensation.  *3 

-33333—  23256  ^  ioo== 

•33333 
about  30  per  cent,  (clearance  neglected). 

Again,  suppose  we  have  a  throttle  governed  engine  cutting  off 
at  two-thirds  the  stroke,  with  an  initial  pressure  of  50  pounds, 
gage, =65  absolute,  running  non-condensing,  it  would  make, 
theoretically,  the  diagram  indicated  by  the  solid  lines  in  Fig.  9, 
and  exert  a  mean  effective  pressure  of  45.62  pounds.  If  we  put 
on  a  condenser  and  reduce  the  back  pressure  to  3  pounds,  in  which 
case  we  should  as  before  realize  a  vacuum  of  12  pounds  or  24 
inches,  the  cut-off  would  remain  at  two-thirds,  but  the  initial 
pressure  would  be  lowered,  as  shown  by  the  dotted  lines,  to  38 
pounds.  While  the  volume  up  to  cut-off  is  the  same  in  each  case, 
95  lbs.absolute  the  pressure  is  lowered,  and 

the  same  volume  of  lower 
pressure  steam  weighs  less. 
^  Suppose  the  size  of  the 
cylinder  was  such  that  it 
took  a  cubic  foot  to  fill  it  up 
to  cut-off.  Then,  when 
making  the  non-condens- 
absolute  zero  Power. s. t.  ing  diagram  shown  by   the 

Fig.  9.  solid    lines    in   Fig.    9,    it 

would  take  a  cubic  foot  of  50- pound  steam  (65  absolute)  which 
would  weigh  .1519  of  a  pound.  When  making  the  condensing 
diagram  shown  by  the  dotted  lines,  it  would  take  the  same 
volume  of  53-pound  (absolute)  steam,  which  would  weigh  .1255 
of  a  pound.     An  apparent  saving  of 

•I5I9  -I255  ><  100  =  17.38  per  cent. 
.1519 
This  is  not,  however,  a  pure  saving.  The  most  important 
charge  against  it  is  the  reduction  of  available  temperature  for  the 
feed  water.  With  an  engine  exhausting  at  atmospheric  pressure 
the  exhaust  steam  has  a  temperature  of  2120,  and  by  the  use  of  a 
suitable  heater  it  is  possible  to  get  the  feed  water  nearly  as  hot. 
With  a  condenser  in  which  the  absolute  pressure  is  reduced  to 
three  pounds,  the  temperature  of  the  exhaust  steam  is  only 
141  62,  and  the  temperature  of  the  hot- well,  or  the  discharge 
from  the  air-pump,  would  be  in  practice  from  no°  to  1200.  Very 


ATMOSPHERIC  LINE 


14  Loss  in  Feed  Water  Temperature. 

careful  practice  might  raise  it  to  1300  but  the  temperature  of  the 
hot-well  will  always  be  considerably  less  than  that  due  to  the 
pressure  of  the  steam  or  vapor  in  the  condenser,  on  account  of 
the  impossibility  of  bringing  every  particle  of  steam  into  contact 
with  the  water  when  only  the  exact  quantity  of  water  theoreti- 
cally needed  to  condense  it  is  used,  and  the  raising  of  the  pres- 
sure in  the  condenser  by  the  presence  of  air  without  a  corres- 
ponding increase  of  the  temperature.  Suppose  the  hot-well  tem- 
perature is  no°  as  against  the  2100  that  we  might  have  by  run- 
ning non-condensing.  There  would  be  a  loss  of  approximately 
10  per  cent,  for  there  is  a  gain  in  efficiency  of  one  per  cent  for 
about  each  ten  degrees  we  heat  the  feed  water.  Even  if  we  kept 
the  hot- well  up  to  1300  there  would  be  a  fall  in  the  available  tem- 
perature of  feed  of  8o°,  or  approximately  eight  per  cent. 

Again,  it  takes  a  great  deal  of  water  to  condense  the  steam, 
and  all  this  water,  as  well  as  the  condensed  steam  and  the  air, 
which  has  worked  in  with  it  and  by  leakage,  must  be  pumped  out 
against  the  pressure  of  the  atmosphere,  so  that  the  cost  of  sup- 
plying the  condenser  with  water  and  of  operating  the  air  pump 
must  be  deducted  from  the  apparent  gain.  There  is  also  the  in- 
terest on  the  extra  cost  of  the  condenser,  the  extra  repairs,  sup- 
plies, insurance  and  attendance  if  the  condenser  plant  is  large 
enough  to  require  especial  attention. 

Here  is  a  little  extract  from  Peabody's  Steam  Tables,  giv- 
ing the  amount  of  the  heat  contained  in  a  pound  of  steam  at 
absolute  pressures  of  from  10  to  25  pounds,  or  from  about  5 
pounds  below  the  atmosphere  to  about  10  pounds  above.  The 
column  marked  "Heat  of  the  Liquid"  gives  the  number  of 
heat  units  that  we  would  have  to  put  into  a  pound  of  water 
to  bring  it  from  32 °  up  to  the  boiling  point  (given  in  the 
second  column),  at  the  corresponding  pressure  in  the  first  col- 
umn. It  is  unnecessary  to  tell  those  of  you  who  have  read  the 
previous  lectures  that  a  "heat  unit"  or  "British  Thermal  Unit" 
is  the  amount  of  heat  necessary  to  raise  a  pound  of  water  one  de- 
gree. In  the  column  marked  "Heat  of  Vaporization"  is  given 
the  "latent  heat"  or  the  number  of  heat  units  necessary  to  evap- 
orate the  pound  of  water  into  steam  after  it  has  been  raised  to  the 
boiling  point.  The  "Total  Heat"  is  the  sum  of  the  two.  Now 
suppose,  the  terminal  pressure  in  the  cylinder,  that  is,  the.  pres- 


Water  Required  to  Condense  a  Pound  of  Steam. 


*5 


sure  at  the  time  the  exhaust  valve  opens,  is  5  pounds  above  the 
atmosphere,  or  say  20  pounds  absolute,  then  every  pound  of  steam 
used  will  carry  to  the  condenser  1151.5  heat  units.  Suppose  the 
hot- well  temperature  is  1200.  A  pound  of  water  at  1200  con- 
tains 88.1  heat  units  above  320 .  Suppose  again  that  the  tem- 
perature of  the  injection  water  was  6o°  .  A  pound  of  water  at 
6o°  contains  28.12  heat  units  above  320  .  Then  each  pound  of 
water  in  raising  from  60  to  1200  will  absorb  88.1  —  28.12  =  59.88 
heat  units. 

To   condense  the  pound  of  steam  and  reduce  it  to  water  of 
1200  we  must  take  from  it   1151.5  —  88.1=  1063.4  heat  units. 


A 

4ft 

"d 

0" 

Pressure, 
Pounds  per 
Square Inc 

mperature, 
grees 
Fahrenhei 

3 

w 

03 
A 

+3 

CO 
-t-a 

c 

CM   O 

OS 

3  J 

03  Fh 

«| 

03  13 

HA 

O 

O 

> 

10 

193  25 

1619 

1140.9 

979.0 

11 

197  78 

166  5 

1142  3 

975  8 

12 

201  98 

170  7 

1143.6 

972.9 

13 

205  89 

174.6 

1144.7 

970  1 

14 

209.57 

178.3 

1145  8 

967.5 

15 

213.03 

181.8 

1146.9 

965  1 

16 

216  32 

185  1 

1147.9 

962.8 

17 

219  44 

188  3 

1148  9 

960.6 

18 

222  40 

19!  3 

1149  8 

958.5 

19 

225.24 

194  1 

1150  7 

956.6 

20 

227.95 

196  9 

1151.5 

954.6 

21 

230  55 

199  5 

1152.3 

952  8 

22 

233.06 

202  0 

1153.0 

9510 

23 

235  47 

204  5 

1153  7 

949.2 

24 

237.79 

206  8 

1154.4 

947  6 

25 

240  04 

209  1 

1155.1 

946  0 

As  one  pound  of  water  will  absorb  59.88  units  it  will  require  to 

condense  each  pound  of  steam 

1063.4  ~^~  59-88  =  17.7  pounds  of  injection  water. 

It  will  be  noticed  that  the  number  of  heat  units  absorbed  by 
one  pound  of  water  is  very  nearly  the  difference  in  temperature 
between  the  injection  water  and  the  hot-well.  This  difference 
in  the  case  in  question  would  have  been  120  —  60  =  60  heat 
units,  and  is  near  enough  in  any  case  for  practical  purposes.  To 
find  the  amount  of  water  required  for  a  condenser,  subtract  the 


1 6  Cooling   Water  Required  for  a  Given   Engine. 

heat  units  contained  in  a  pound  of  water  at  the  hot-well  temper- 
ature from  the  number  of  such  units  contained  in  a  pound  of 
steam  of  the  terminal  pressure.  These  values  can  be  gotten  from 
a  table  of  the  Physical  Properties  of  Steam,  to  be  found  in  any 
engineer's  reference  book.  Divide  this  value  by  the  difference 
between  the  temperature  of  the  injection  and  of  the  hot- well,  or 
by  the  rise  in  temperature  of  the  circulating  water  in  the  case  of 
the  surface  condenser,  and  you  get  the  number  of  pounds  of  in- 
jection or  circulating  water  required  per  pound  of  steam.  Mul- 
tiply this  by  the  number  of  pounds  of  steam  required  per  hour 
per  horse-power,  and  you  get  the  injection  per  hour  per  horse- 
power. Multiply  this  again  by  the  horse- power  developed,  and 
you  get  the  injection  required  to  run  a  given  engine  with  a  given 
load. 

When  the  only  water  available  for  injection  is  foul,  and  would 
make  a  mixture  in  the  hot- well,  that  would  not  do  to  feed  to  the 
boilers, '  a  surface  condenser  may  be  used.  This  is  the  general 
practice  on  sea-going  steamers  where  the  injection  water  is  salt, 
and  it  is  necessary  to  use  the  same  boiler  water  over  and  over. 
Did  you  ever  think  what  an  immense  amount  of  water  is  boiled 
into  steam  to  run  one  of  the  great  liners  ?  The  Paris  has  30,000 
horse-power.  Suppose  she  runs  on  13  pounds  of  steam  per  hour 
per  horse-power,  her  boilers  would  evaporate  over  a  million  gal- 
lons of  water  a  day,  a  good  supply  for  a  sizable  town.  Of  course 
they  cannot  afford  to  foul  this  by  mixing  the  salt  sea  water  with 
it,  so  they  condense  it  by  letting  it  come  in  contact  with  metal 
surfaces  kept  cool  by  sea  water  flowing  upon  the  other  side,  but 
always  separated  from  the  condensed  steam.  In  this  way  it  will 
be  seen  the  cooling  or  circulating  water  is  kept  entirely  separate 
from  the  condensed  steam  and  the  latter  can  be  safely  returned 
to  the  boilers,  while  any  sort  of  non-corrosive  liquid  can  be  used 
for  cooling  purposes.  We  have  heard  of  plants  in  large  cities 
where  water  was  taken  from  the  sewer,  passed  through  a  surface 
condenser,  and  returned  to  the  sewer  again. 

It  will  be  noticed  that  the  exhaust  steam  carries  to  the  conden- 
ser a  very  large  percentage  of  the  heat  which  it  brings  from  the 
boiler.  A  pound  of  steam  at  80  pounds  gage,  95  absolute,  con- 
tains 1 1 80. 7  heat  units.  Suppose  20  pounds  of  this  steam  are 
required  per  hour  per  horse-power.     Then  20  pounds  of  steam 


Where  a  Condenser  is  not  Advisable.  17 

will  do  33,000  X  60  —  1,980,000  foot  pounds  of  work,  one  pound 
will  do  1,980,000-1-20=  99,000  foot  pounds.  As  one  heat  unit 
is  equal  to  778  foot  pounds,  the  number  of  heat  units  transformed 
to  work  would  be  99,000 -f-  778=127. 4  heat  units. 
1180.7  —  127.4  =  1053.3. 
We  have  1 180.7  units  of  heat  taken  from  the  boiler,  127.4  of 
them  converted  into  work  and  the  balance,  barring  the  trifling 
loss  from  radiation,  going  out  in  the  exhaust.  It  follows  that  if 
we  have  any  use  for  heat  at  anything  under  the  temperature  of  a 
reasonable  exhaust,  it  would  be  bad  engineering  to  let  this  heat, 
which  might  be  applied  to  the  purpose,  escape  into  the  river  in 
the  overflow  from  a  hot-well.  One  case  then  where  it  is  inad- 
visable to  use  a  condenser  is  where  it  is  possible  to  use  the  ex- 
haust steam  to  advantage. 

Again,  suppose  we  had  80  pounds  initial  pressure  and  instead 
of  cutting  off  at  one  quarter  we  carried  the  80  pounds  for  the  full 
stroke,  and  exhausted  at  atmospheric  pressure  our  mean  effective 
pressure  would  be  80  pounds.  Now,  if  we  put  on  a  condenser 
giving  us  12  pounds  of  vacuum,  we  must  reduce  the  initial  to  68 
pounds  gage.  The  volumes  used  would  be  the  same  in  both 
cases.  Steam  of  80  gage  (95  absolute)  pressure  weighs  .2165  of 
a  pound;  at  68  pounds  gage  (83  absolute),  .1908,  a  saving  of 

.2165  .1 90S  vy  0 

- - — X  100=  1 1. 8  per   cent. 

.2165 

Now  if  we  lose  ten  per  cent  by  reducing  the  temperature  of 
our  feed  water,  and  it  takes  two  per  cent  to  run  the  air  pump,  we 
shall  be  worse  off  with  the  condenser,  than  without  it,  to  say 
nothing  of  the  investment  in  it,  the  cost  of  oiling,  packing,  at- 
tending it,  and  keeping  it  in  repair.  Evidently  here  is  another 
case  where  we  would  be  better  off  without  the  condenser. 

In  a'  well-designed  engine,  the  power  required  to  operate  the 
pumps  may  be  less  than  one  per  cent  of  that  developed  by  the 
main  engine,  and  is  sometimes  as  high  as  three  per  cent.  This 
percentage  or  more  of  the  steam  supplied  may  be  used  according 
as  the  pump  is  operated  from  the  engine  itself,  or  by  an  inde- 
pendent cylinder  more  extravagant  in  the  use  of  steam. 

In  order  to  understand  one  of  the  points  that  bears  on  the  de- 
sirability of  the  condenser  in  a  special  case,  it  is  necessary  to  un- 


1 8  Effect  of  Cylinder  Condensation. 

derstand  something  of  the  cylinder  condensation.  When  steam 
contains  just  the  number  of  heat  units  per  pound  given  in  the 
tables,  that  is,  just  enough  to  evaporate  it  into  steam,  it  is  said  to 
be  "saturated."  This  means  that  it  is  saturated  with  heat,  not 
with  moisture.  The  term  is  apt  to  be  misunderstood,  and  I  have 
frequently  talked  with  engineers  who  could  not  get  rid  of  the 
idea  that  "saturated"  steam  must  be  soaking  wet.  The  ordin- 
ary steam  that  we  get  from  boilers  carries  with  it  more  or  less 
moisture,  and  steam  is  "commercially  dry"  when  it  has  no  more 
than  two  per  cent  by  weight  of  such  moisture.  If  we  apply  heat 
to  such  steam,  and  dry  it  out  or  evaporate  the  moisture,  we  shall 
have  "saturated"  steam  at  the  instant  that  all  the  moisture  is 
gone,  and  if  we  continue  the  heating  so  as  to  increase  the  tem- 
perature above  that  due  to  the  pressure,  we  shall  have  '  'super- 
heated" steam. 

Now,  unless  steam  is  superheated,  it  cannot  lose  a  particle  of 
heat,  except  by  expansion,  without  a  corresponding  amount  of 
condensation.  Steam'  of  80  pounds  gage  (95  absolute)  pressure 
has  a  temperature  of  about  3240  F.  As  it  is  expanded  in  the 
cylinder  after  cut-off  its  temperature  falls,  and  during  the  ex- 
haust stroke  the  temperature  is  that  due  to  the  back  pressure; 
2120  if  the  exhaust  is  against  the  atmosphere,  141. 6°  with  a  con- 
denser reducing  the  absolute  back  pressure  to  3  pounds.  As  a 
consequence,  the  cylinder  and  piston  heads,  the  ports,  and  wall 
of  the  cylinder,  having  been  in  contact  with  this  cooler  steam, 
have  had  their  temperature  reduced  and  when  the  live  steam  en- 
ters at  the  beginning  of  the  stroke,  it  finds  itself  in  contact  with 
surfaces  comparatively  chilly,  and  therefore  has  to  part  with 
enough  heat  to  raise  these  surfaces  to  its  own  temperature  before 
it  can  continue  to  exist  as  steam  in  contact  with  them.  As  a  re- 
sult, there  is  a  large  amount  of  condensation  at  the  beginning  of 
the  stroke,  and  this  continues  up  to  the  point  of  cut-off.  As  the 
steam  commences  to  expand  its  temperature  is  reduced,  the  sur- 
faces begin  to  give  back  the  heat  that  has  been  expended  upon 
them,  and  the  water  resulting  from  the  initial  condensation  com- 
mences to  boil  under  the  diminished  pressure,  as  did  the  water 
when  we  cooled  the  flask  in  lecture  I.  Meantime,  however,  the 
piston  is  uncovering  new  cylinder  wall,  which  requires  to  be 
heated,  and  this  action  will  continue  to  a  point  where  the  temper- 


Effect  q/  Cylinder  Condensation.  19 

ature  which  the  wall  has  assumed  equals  the  temperature  of  the 
expanding  steam.  Beyond  this  point  all  the  surfaces  are  hotter 
than  the  steam  and  the  re- evaporation  is  more  rapid.  Except  on 
very  slow  running  engines,  however,  this  re-evaporation  during 
the  working  stroke  is  not  very  extensive.  In  a  good  tight  en- 
gine at  ordinary  speeds  the  expansion  line  usually  agrees  very 
well  with  the  theoretical  curve,  commonly  rising  a  little  above  it 
at  the  later  portion,  showing  that  the  re-evaporation  but  little 
more  than  makes  up  for  the  condensation  due  to  the  conversion 
of  some  of  the  heat  units  into  work,  and  to  radiation.  In  this 
way  the  re-evaporation  during  the  working  stroke  is  a  benefit, 
but  the  greater  part  of  the  evaporation  occurs  during  the  exhaust 
stroke,  when  the  resulting  steam  can  do  no  good,  but  is  escap- 
ing to  the  atmosphere,  or  the  condenser.  When  the  pressure  is 
reduced  by  the  opening  of  the  exhaust  valve,  the  moisture  in  the 
cylinder,  being  above  the  boiling  point  at  the  reduced  pressure, 
passes  rapidly  into  steam,  the  heat  for  its  continued  evaporation 
being  furnished  by  the  containing  surfaces,  and  these  containing 
surfaces  chilled  by  this  abstraction  of  heat,  must  be  heated 
again  on  the  following  stroke.  The  wall  never  gets  as  cool  as 
the  exhaust  temperature,  and  probably  never  as  hot  as  the  in- 
itial steam.  The  longer  the  time  it  is  exposed  to  a  temperature 
lower  than  the  initial  and  the  lower  the  temperature  of  the  ex- 
haust, the  greater  will  be  its  range  of  variation.  Notice  that 
the  surfaces  must  give  up  to  the  outgoing  steam  exactly  as 
much  heat  as  they  receive  from  the  incoming  steam.  They  cer- 
tainly cannot  give  up  any  more,  and  if  they  did  not  give  up  as 
much  as   they  got,  heat  would  accumulate  and  melt  them  down. 

This  subject  of  cylinder  condensation  is  one  of  the  most  inter- 
esting and  important  connected  with  steam  engineering.  Exper- 
iments indicate  that  the  loss  from  this  action  is  rarely  less  than 
20  per  cent  in  simple  unjacketed  cylinders  of  ordinary  automatic 
engines,  and  it  may  be  much  more.  The  point  I  want  to  call 
your  attention  to  in  connection  with  our  present  subject  is  that 
the  greater  the  difference  between  the  initials  and  back  pressures, 
the  hotter  the  steam  the  cooler  the  exhaust,  the  greater  this  ac- 
tion and  loss  will  be.  Further,  the  earlier  in  the  stroke  the  cut- 
off occurs  the  greater  the  initial  condensation,  because  of  the 
greater  variation  of  temperature  on  the  working  stroke  and  the 


2o  Diagram  of  Maximum  Efficiency. 

greater  proportion  of  the  time  that  the  temperature  of  the  steam 
in  the  cylinder  is  below  that  of  the  steam  chest.  The  condensa- 
tion will  also  increase  wTith  any  increase  in  the  proportion  which 
the  area  of  the  containing  surface  bears  to  the  volume  of  steam 
contained. 

In  an  indicator  diagram  like  Fig.  10,  the  space  E  B  represents 
the  volume  of  the  cylinder  including  clearance  up  to  the  point  of 
cut-off,  while  the  shaded  area  is  proportional  to  the  work  done. 
The  volume  that  must  be  filled  with  steam  at  each  stroke  will 
bear  the  smallest  proportion  to  the  work  done  when  as  in  Fig.  3 
the  cut-off  is  at  such  a  point  that  expansion  extends  just  to  the 
line  of  back  pressure,  making  the  diagram  end  in  a  point;  and 
compression  extends  just  to  initial  pressure.  The  higher  the  in- 
itial pressure  and  the  lower  the  back  pressure,  the  greater  will  be 
the  number  of  expansions  used,  and  the  greater  the  area  of  the 
diagram  compared  with  the  ^  a  b 
volume  up  to  cut-off.  But 
every  engineer  knows  that, 
notwithstanding  the  fact 
that  the  steam  accounted 
for  by  the  diagram  per 
horse-power  would  be  the 
least  in  amount  under  these  .  *N**r. 

conditions,  it  would  be  very  ^>'  IO' 

poor  economy  to  run  an  engine  with  so  light  a  load.  We  might 
continue  the  reduction  of  the  diagram  on  these  lines  until  the  power 
developed  is  barely  sufficient  to  run  the  engine  itself,  in  which  case, 
even  if  we  got  a  very  low  rate  of  steam  consumption  per  indicated 
horse-power,  the  little  useful  power  we  would  get  would  be  very 
expensive.  As  a  matter  of  fact,  however,  we  should  use  more 
steam  per  indicated  horse-power,  for  the  gain  by  expansion  falls 
off  rapidly  as  the  number  of  expansions  is  increased,  while  the 
loss  by  cylinder  condensation  increases  at  a  rapid  rate.  Conse- 
quently, there  is  a  point  where  the  loss  from  cylinder  condensation 
equals  the  gain  from  increased  expansion,  and  any  increase  of  ex- 
pansion will  result  in  a  loss.  The  more  power  we  can  get  out 
of  the  cylinder  the  less  proportion  will  the  radiation  and  frictional 
losses  bear  to  the  power  delivered  to  the  shafting,  so  that  it  is  not 
found  economical   in  practice  to  cut  off  much  earlier  than  one- 


•  Independent  and  Direct  Driven   Condensers.  21 

quarter  stroke,  in  an  ordinary  single-cylinder  non-condensing  en- 
gine without  jackets;  nor  to  expand  much  below  the  atmosphere 
with  a  simple  condensing  engine.  Obviously  then,  if  an  engine 
is  cutting  off  at  one- fifth  stroke,  or  earlier,  there  will  be  little 
chance  of  increasing  the  economy  by  putting  on  a  condenser.  It 
is  possible  to  extend  the  point  of  cut-off  without  increasing  the 
mean  effective  pressure  by  lowering  the  boiler  pressure,  or  throt- 
tling it  at  the  engine,  but  here  the  efficiency  of  the  high  pressure 
steam  is  sacrificed,  and  it  is  still  an  open  question  how  far  it  is 
safe  to  go  in  this  direction.  I  commend  it  to  you  as  a  subject  for 
profitable  discussion,  whether  with  an  underloaded  engine,  con- 
densing or  not,  it  is  profitable  to  reduce  the  initial  pressure  and 
if  so  under  what  circumstances  and  to  what  extent. 

Condensers  may  be  divided  into  two  general  classes.  Those 
whose  air  pumps  are  driven  by  the  main  engine. 

Those  having  their  own  independent  motive  power. 

The  first  type  includes  belt  and  gear  driven  pumps  as  well  as 
those  directly  attached  to  the  working  parts  of  the  engine  itself. 
The  advantage  claimed  for  them  is  that  the  power  required  to 
drive  them  is  generated  in  the  large  economical  cylinder  to  much 
better  advantage  that  it  can  be  in  a  small  cylinder  of  a  direct  act- 
ing pump,  such  as  is  usually  used  to  operate  the  independent  con- 
denser. 

On  the  other  hand,  the  advocates  of  the  independent  conden- 
ser claim  that  while  the  attached  air  pump  is  constrained  to  move 
at  the  same  speed  as  the  main  engine  or  a  speed  proportional 
thereto,  regardless  of  the  amount  of  work  it  has  to  do,  the  inde- 
pendent air  pump  can  be  run  fast  or  slow  according  to  the  amount 
of  water  passing,  which  varies  with  the  load  and  the  vacuum  car- 
ried. They  further  claim  that  the  steam  from  the  cylinders 
which  operate  the  pump  can  be  used  to  heat  the  feed-water,  thus 
doing  away  with  1  he  loss  noted  above,  and  that  as  practically  all 
the  steam  required  to  run  the  pump  is  thus  utilized,  it  does  not 
matter  if  the  pump  is  not  so  economical  as  the  main  engine. 
Many  of  both  types  of  condenser  are  used  and  each  has  its  ad- 
vocates. If  one  is  very  decidedly  better  than  the  other,  it  will 
in  time  appear,  and  the  fittest  will  survive  or  perhaps  as  in  many 
other  cases  it  will  be  found  that  each  is  particularly  adapted  to 
special  circumstances. 


^2 


The    Vertical  Air  Pnmt>. 


The  amount  of  work  done  by  an  air  pump  depends  not  upon 
the  size  of  the  piston,  or  the  speed  at  which  it  runs,  but  upon  the 
amount  of  water  and  air  that  it  forces  out  of  the  condenser 
against  the  pressure  of  the  atmosphere.  In  Fig.  n,  when  the 
bucket  or  piston  rises,  it  leaves  a  vacuum  behind  it.  Suppose 
that  the  water  line  A  B  just  reached  the  diaphragm  CD  when 
the  bucket  was  in  its  highest  position,  without  lifting  the  valves. 
Then  when  the  bucket  descended  it  would  leave  a  vacuum  above 
it,  and  if  no  water  is  let  in  to  raise  the  level  A  B  the  bucket  will 
continue  to  move  up  and  down  with  a  vacuum  above  and  below 
it,  without  doing  any  work  or  calling  for  any  power  except  to 
overcome  its  own  friction.  Now  if  we  let  a  little  water  into  the 
chamber  B,  a  corresponding 
amount  will  pass  through  the 
bucket  on  its  downward  stroke, 
increasing  the  amount  above 
the  bucket  and  the  water  line 
A  B  will  come  in  contact  with 
the  diaphragm  C  D  before  the 
upward  stroke  is  completed, 
lifting  the  valves  in  that  dia- 
phragm, andmaking  the  pump 
complete  the  stroke  against 
the  atmospheric  pressure.  /7^ 
This  is  where  the  work  of  the 
pump  comes  in,  and  this  will 
be  dependent  upon  the  quanti- 
ty of  water  passed,  for  if  we  p^  II# 
put  in  twice  the    amount   of 

water,  the  valves  in  C  D  will  be  open  twice  as  long  and  the  bucket 
travel  twice  as  far  against  the  atmospheric  pressure.  Of  course 
there  would  be  a  saving,  so  far  as  friction  is  concerned,  if  the 
pump  could  be  run  slowly  enough  to  completely  fill  at  each  stroke, 
instead  of  making  several  strokes  to  do  an  equivalent  amount  of 
work,  but  it  is  not  constantly  working  against  a  vacuum  as  many 
suppose. 

It  is  quite  generally  conceded  that  the  vertical  form  of  air 
pump,  although  necessarily  single  acting,  is  preferable  to  the 
double  acting  horizontal  pump.     This  is  due  to  the  certainty  of 


Sealed  Glands — Surface  Condensers  23 

its  action  in  taking  water  through  the  bucket  valves,  to  the 
quick  and  positive  closure  of  the  valves,  to  the  facility  with 
which  the  water  will  collect  in  the  bottom  of  the  pump  during 
the  up  stroke  ready  for  the  bucket  when  it  descends.  The  flow 
is  always  in  one  direction,  the  water  always  lies  on  the  valves 
so  as  to  keep  them  air  tight,  and  very  little  clearance  is  necessary 
between  the  foot  and  bucket  valves  and  between  the  bucket  and 
head  valves.  The  glands  around  the  vertical  rods  can  be  cupped 
and  filled  with  water,  to  seal  them  against  air  leaks.  It  don't 
hurt  a  vacuum  any  to  have  water  leak  into  it,  but  a  little  air  will 
make  a  big  difference,  so  that  if  you  can  keep  water  around  a 
place  where  air  is  likely  to  get  in  you  will  have  a  better  vacuum. 
I  have  heard  of  serious  breaks  in  condensing  apparatus  being  got- 
ten over  at  sea  by  building  a  coffer  dam  around  the  fracture  and 
keeping  it  full  of  water.  This  kept  it  sealed  against  the  atmos- 
phere, and  some  water  simply  went  through  the  crack  instead  of 
through  the  injection  valve. 

Of  course  the  air  pump  must  be  large  enough  to  keep  the  con- 
denser clear  at  times  of  maximum  load  or  when  the  greatest 
amount  of  water  and  air  is  to  be  handled.  On  the  other  hand,  it 
should  not  be  too  large  so  as  to  cause  unnecessary  loss  by  fric- 
tion. The  indications  are  that  past  practice  has  been  too  liberal 
in  this  respect  and  that  many  engines  have  labored  along  with 
cumbersome  pumps  where  smaller  sizes  would  have  been  ample. 
It  would  appear,  too,  that  good  design  lies  in  the  direction  of 
short  strokes  and  large  diameters,  for  if  we  quarter  the  stroke  of 
a  pump  and  double  its  diameter,  it  will  have  the  same  capacity, 
the  force  required  to  overcome  the  friction  will  be  exerted  through 
only  one- quarter  the  space,  and  will  be  no  more  than  twice  what 
it  was  before  for  the  rubbing  surface,  the  circumference  of  the 
bucket  has  only  been  doubled,  and  in  a  vertical  pump  where  the 
bucket  is  always  covered  with  water,  this  may  be  an  easy  fit. 
The  larger  bucket  also  gives  greater  capacity  for  the  valves  and 
the  speed  of  the  water  through  the  larger  passages  thus  afforded 
is  slower. 

If  you  are  interested  in  proportioning  surface  condensers,  I  ad- 
vise you  to  read  a  paper  on  the  subject  by  J.  M.  Whitham,  page 
417,  Vol.  IX.,  Trans.  Amer.  Soc.  Mech.  Engrs.  In  it  he  consid- 
ers all  the  factors  bearing  on  variable  conditions  and  gives  formu- 


24 


The  Injector  Condenser. 


lae  which  meet  all  conditions.     For  the  average  case,  he  gives  a 
very  simple  formula  for  the  amount  of  cooling  surface  required. 

Multiply  the  total  number  of  pounds  of  steam  conde?ised  per 
hour  by  ij  and  divide  by   180. 

This  allows  nearly  one-tenth  of  a  square  foot  of  cooling  surface 
per  pound  of  steam,  which  would  not  be  a  bad  figure  to  bear  in 
mind. 

A  condenser  may  fail  to  work  from  a  failure  of  the  injection  or 
circulating  water  supply,  in  which  case  the  steam  will  not  be  con- 
densed, but  will  accumulate  in  the  condenser,  destroying  the  vac- 
uum and  heating  the  condenser 
up.  Relief  valves  which  open 
automatically  to  the  atmos- 
phere when  the  pressure  in 
the  condenser  exceeds  that 
outside  are  usually  provided 
to  allow  the  engine  to  keep  on 
running  non- condensing  until 
the  trouble  can  be  located  and 
remedied.  Secondly,  a  con- 
denser may  fail  to  work  on  ac- 
count of  the  failure  of  the  air 
pump  to  remove  the  water  and 
air  as  fast  as  it  comes  to  the 
condenser.  Such  a  failure  is 
apt  to  result  seriously,  for  if 
there  should  be  a  vacuum  in 
the  cylinder  at  such  a  time, 
as  there  is  likely  to  be  by  expansion  in  the  low  pressure  cylinder 
of  a  compound  or  triple  expansion  engine,  or  even  in  a  single 
cylinder  engine  when  starting  or  stopping,  or  when  lightly  loaded, 
the  water  will  draw  into  it  and  result  in  a  break  down.  For  this 
reason  condensers  are  often,  and  should  always  be  provided  with 
a  device  for  automatically  admitting  air  and  breaking  the  vacuum 
when  the  height  of  water  in  the  condensing  chamber  exceeds  a 
safe  limit,  and  care  must  be  taken  that  nothing  occurs  to  slow 
down  the  air  pump  if  indirectly  connected  or  independent. 

You  remember  the  experiment  we  performed  with  the  long 
tube  of  mercury.     The  action  would  be  just  the  same  with  water 


Fisr.   12. 


The  Injector  Condenser. 


25 


RELIEF  VALVE 


enly  it  would  take  a  longer  column  of  water  to  balance  the  pres- 
sure of  the  atmosphere.  In  Fig.  12,  if  the  tank  were  originally 
full  of  water,  the  water  would  run  out  through  the  pipe  until  the 
column  is  just  sufficient  to  balance  the  pressure  of  the  atmos- 
phere, which  will  be  34  feet  more  or  less  according  to  the  tem- 
perature of  the  water  and  the  height  of  the  barometer.  If,  then, 
we  have  the  pipe  over  34  feet  long,  water  will  run  out  of  the 
chamber  by  its  own  weight  against  the  atmospheric  pressure, 
leaving  a  vacuum  in  the  chamber.  If  we  let  steam  and  cool 
water  together  into  such  a  chamber,  the  steam  would  be  con- 
densed, the  water  would  flow  out  without 
the  necessity  of  a  pump,  and  the  vacuum 
would  be  maintained  without  the  bother 
and  expense  of  pumping  the  water  out. 
There  is  one  fatal  objection  to  the  opera- 
tion of  this  ideal  scheme.  We  have  seen 
that  the  steam  and  the  injection  water 
bring  into  the  condenser  more  or  less  air 
to  say  nothing  of  that  which  steals  in 
through  leakage.  *As  the  air  would  not 
fall  out  by  gravity,  it  would  gradually  ca- 
cumulate  and  destroy  the  vacuum.  This 
objection  is  very  ingeniously  and  simply 
gotten  over  in  the  injector  or  ejector  con- 
denser, shown  in  Fig.  13.  The  exhaust 
steam  enters  through  the  nozzle  A.  The 
injection  water  surrounds  this  nozzle  and 
issues  downward  through  the  annular 
space  between  the  nozzle  and  the  main 
casting.  The  steam  meeting  the  water  is 
condensed,  and  by  virtue  of  its  weight  and  of  the  momentum  which 
it  has  acquired  in  flowing  into  the  vacuum  the  resulting  water 
continues  downward,  its  velocity  being  further  increased,  and  the 
column  solidified  by  the  contraction  of  the  nozzle  shown.  The  air 
is  in  this  way  carried  along  with  the  water  and  it  is  impossible 
for  it  to  get  back  against  the  rapidly  flowing  steam  in  the  con- 
tracted neck.  The  condenser  will  lift  its  own  water  twenty  feet 
or  so.  When  water  can  be  had  under  sufficient  head  to  thus  feed 
itself  into  the  system,  and  the  hot- well  can  at  the  same  time  be 


26  Cooling    Towers.      Co?idensi?ig  by  Evaporatioii. 

so  situated  as  to  drain  itself,  it  makes  a  remarkably  simple  and 
efficient  arrangement.  In  case  the  elevation  is  so  great  that  a 
pump  has  to  be  used  to  force  the  injection,  the  pump  has  to  do 
less  work  than  the  ordinary  air  pump,  and  its  exhaust  can  be 
used  to  heat  the  feed  water. 

Except  under  exceptional  circumstances,  the  nature  of  which 
we  have  tried  to  indicate,  the  gain  by  the  use  of  a  condenser  is  so 
great  that  their  use  is  very  general  in  plants  where  water  can  be 
had  for  condensing  purposes,  and  it  is  an  important  point  for  con- 
sideration in  locating  a  plant,  whether  or  not  a  supply  of  suitable 
condensing  water  will  be  available.  In  large  cities  where  water 
must  be  bought  at  a  considerable  cost,  plants  are  run  non- con- 
densing at  a  great  sacrifice  of  steam  efficiency,  because  it  would 
be  out  of  the  question  to  buy  water  for  injection.  Considerable 
has  been  done  in  the  way  of  cooling  water  off  after  it  has  passed 
through  the  condenser,  and  using  it  over  and  over  again.  This 
is  done  by  letting  it  trickle  over  a  series  of  pans  on  the  roof,  or 
letting  it  fall  in  a  shower  through  a  shaft  through  which  a  cur- 
rent of  air  is  circulated. 

In  this  connection,  there  has  recently  appeared  on  the  market, 
an  apparatus,  which  appears  to  promise  well.  You  know  as  much 
heat  must  be  taken  out  of  a  pound  of  steam  to  reduce  it  to  water 
of  a  given  temperature,  as  would  have  to  be  put  into  the  water  to 
make  it  into  steam  from  that  temperature.  Suppose  the  steam 
from  an  engine  cylinder  is  discharged  through  a  series  of  pipes 
upon  the  outside  of  which  cold  water  is  sprayed.  Part  of  the 
water,  as  it  strikes  the  heated  surface,  will  be  evaporated  and  es- 
cape into  the  atmosphere  as  vapor,  but  for  every  pound  of  water 
so  evaporated  a  pound  of  steam  is  condensed,  and  can  be  used  as 
boiler  feed.  Thus,  instead  of  using  the  city  water  for  boiler  feed, 
we  use  it  to  spray  the  condenser,  and  use  the  condensed  steam 
over  and  over  in  the  boilers,  and  if,  as  it  appears,  and  as  the  mak- 
ers of  the  apparatus  assure  us,  it  takes  no  more  water  in  one 
case  than  in  the  other,  we  are  ahead  whatever  net  benefit  we  can 
get  out  of  the  vacuum. 

It  is  a  mistake  to  strain  for  too  high  a  vacuum.  Of  course 
every  particle  that  you  can  save  by  keeping  things  free  from  air 
leakage  is  so  much  pure  gain.  What  I  mean  is  don't  crowd  your 
circulating  pump  or  open  your  injection  too  wide  just  to  get  the 


Situation  of  Pump.     Lifting    Valves.  27 

last  fraction  of  an  inch  of  vacuum.  The  amount  of  water  to  be 
handled  to  get  an  additional  half  inch  at  the  lower  end  of  the 
gage  is  excessive,  the  temperature  of  your  feed  is  reduced,  and 
while  it  may  mean  less  pounds  of  steam  per  hour  per  horse- power 
for  the  main  engine,  it  is  likely  to  mean  more  dollars  per  year 
per  useful  horse-power  delivered.  If  you  do  not  use  the  hot-well 
water  for  boiler  feed,  or  if  you  have  methods  by  which  this  may- 
be heated,  that  would  allow  you  to  run  a  lower  hot- well  tempera- 
ture to  advantage.  Suppose,  for  instance,  you  have  an  econo- 
mizer of  ample  capacity,  heating  the  water  with  the  waste  of  the 
uptake,  then  it  would  pay  you  to  run  a  higher  degree  of  vacuum, 
for  if  your  economizer  is  ample,  it  will  deliver  the  water  to  the 
boiler  at  about  the  same  temperature  whether  it  comes  to  it  at 
100  or  130,  and,  so  long  as  you  do  not  make  your  pumps  do  as 
much  extra  work  as  the  extra  vacuum  amounts  to,  you  are 
ahead.  When  cold  water  is  used  for  feed  or  when  there  is  a 
very  considerable  difference  between  the  hot- well  and  exhaust 
steam  temperatures,  and  the  hot- well  water  is  used  for  feed,  the 
water  may  be  passed  through  a  heater  placed  between  the  engine 
and  the  condenser.  The  exhaust  will  have  a  temperature  of 
about  1200  and  will  impart  considerable  heat  to  the  feed,  leaving 
so  much  less  for  the  condenser  to  do. 

You  will  understand,  of  course,  from  what  has  been  said  of  the 
nature  of  a  vacuum  and  of  the  nature  of  pumping  that  no  pump, 
however  powerful,  can  lift  water  out  of  the  condenser  by  suc- 
tion because  the  atmosphere  cannot  act  upon  the  water  to  force 
it  up  to  the  pump.  The  pump  must,  therefore,  be  situated  be- 
low the  condenser,  so  that  the  water  can  fall  into  it  by  its  own 
weight  or  head.  Further,  there  must  be  no  chance  for  any  ac- 
cumulation of  air  or  the  pump  will  get  air  bound  and  simply 
work  back  and  forth  without  taking  any  water. 

A  common  annoyance  connected  with  the  running  of  an  air 
pump  is  the  hammering  or  clattering  of  the  discharge  valves,  due 
to  the  variations  in  pressure  as  the  air  and  water  are  discharging. 
This  can  be  avoided  by  connecting  a  small  pipe  with  a  valve  into 
the  passage  leading  from  the  water  cylinder  to  the  delivery  valve, 
and  admitting  a  small  quantity  of  air,  the  amount  to  be  admitted 
being  only  sufficient  to  overcome  the  hammering.  This  air  can- 
not vitiate  the  vacuum  in  the  condenser,  as  it  aids  the  water  in 
keeping  the  inlet  or  foot- valve  closed.  The  pipe  should  extend 
to  an  elevation  greater  than  the  hot-well  for  otherwise  the  water 
and  the  air  will  discharge  from  it  on  the  down  stroke  of  the 
bucket.* 

^Constructive  Steam  Engineering,  J.  M.  Whitham,  p.  464. 


THE  JET  CONDENSER. 


In  Fig.  i  we  have  a  vessel  filled  with  steam  at  atmospheric 
pressure.  Attached  to  it  is  a  U-tube  filled  with  mercury,  open  to 
the  atmosphere  at  the  outer 
end.  As  long  as  the  inside 
and  outside  pressures  are 
equal,  the  mercury  will  be  at 
the  same  level  in  both  legs  of 
the  tube,  as  shown.  If  we 
inject  a  spray  of  cold  water  in- 
to the  vessel  through  pipe  W, 
the  steam  will  be  condensed 
and  will  fall  to  the  bottom, 
occupying  only  the  small 
space  below  the  dotted  line 
AB  in  Fig.  2.  The  space 
above  the  dotted  line  will  now 

be  empty,  or,  in  other 
words,  a  vacuum,  and  since 
the  pressure  on  the  inside  is 
removed,  the  mercury  will 
rise  in  one  leg  of  the  tube 
as  shown.  If  we  continue 
to  supply  steam  and  con- 
densing water  to  the  vessel 
and  draw  out  the  condensed 
steam  and  water  as  fast  as 
it  accumulates,  we  can  main- 
tain a  constant  vacuum  in  the  vessel.  This  was  the  principle 
upon    which  the  early  mining  pumps  were  operated.     The  piston 


Arrangement  of  Jet  Condenser. 


29 


was  drawn  to  the  top  of  its  stroke  by  the  descending  pump 
plunger;  steam  at  atmospheric  pressure  was  admitted  under  the 
piston  and  condensed  by  a  spray  or  jet  of  water,  thus  creating  a 
vacuum.  The  pressure  of  the  atmosphere  then  forced  the  piston 
down,  raising  the  pump  plunger  at  the  other  end  of  the  beam. 

STEAM  FROM  BOILER  OR 
HIGH  PRESSURE  CYLINDER 


The  same  thing  is  done  on  a  larger  scale  and  in  a  more  scien- 
tific manner  by  the  jet  condensing  apparatus  of  today. 

An  entire  apparatus  of  this  type  including  all  pipes  and  valves, 
and  connected  to  an  engine  cylinder,  is  shown  in  cross-section  by 


30  Types  of  Jet  Condensers. 

Fig.  3.  The  engine  piston  is  moving  to  the  left,  and  the  exhaust 
steam  is  passing  out  through  the  lower  left-hand  port  into  the 
exhaust  pipe  and  from  there  into  the  bottle-shaped  condenser. 
As  it  enters  the  condenser  it  meets  a  spray  of  cold  water  issuing 
from  the  injection  pipe  around  the  edges  of  the  cone  S;  this  spray 
condenses  the  steam  and  the  intermingled  steam  and  water  pass 
down  into  the  lower  part  of  the  condenser  and  the  suction  cham- 
ber of  the  air  pump.  This  leaves  a  vacuum  in  the  condenser  and 
exhaust  pipe  and  the  engine  cylinder  up  to  the  piston  face. 
When  the  air  pump  bucket  starts  on  its  upward  stroke,  the 
mingled  air  and  water  pass  by  gravity  up  through  the  foot  valves 
of  the  air  pump.  When  the  air  pump  bucket  descends,  the  water 
and  air  pass  up  through  the  bucket  valves  to  the  upper  side  of 
the  bucket  or  plunger.  The  next  upward  stroke  of  the  bucket 
forces  the  water  out  through  the  head  valves  of  the  pump  into 
the  discharge  pipe,  at  the  same  time  allowing  more  water  and  air 
from  the  condenser  to  pass  up  through  the  foot  valves  into  the 
lower  part  of  the  air  cylinder.  This  action  is  continuous  and  the 
air-pump  speed  must  be  regulated  to  handle  the  condensed  steam, 
the  water  required  to  condense  it  and  the  air  brought  in  by  the 
water. 

L,et  us  consider  some  of  the  general  features  of  the  jet  conden- 
ser, and  particularly  the  apparatus  shown. 

First  among  these  is  the  fact  that  the  injection  or  condensing 
water  and  the  condensed  steam  are  mixed  together.  If  the  con- 
densing water  is  pure  the  air  pump  discharge  is  suitable  for  boiler 
feed,  but  if  the  condensing  water  is  impure,  acidulous  or  salt,  it 
is  evident  that  the  water  discharged  from  the  air  pump  is  unsuit- 
able for  boiler  use.  Second,  there  is  to  be  considered  the  type  of 
air  pump  and  the  means  by  which  it  is  driven.  This  pump  may 
be  of  the  horizontal  or  vertical  type,  single  cylinder  double  acting, 
dDuble  or  twin  cylinder  single  acting  or  duplex;  it  may  be  inde- 
pendently steam  driven,  as  in  Fig.  3,  or  it  may  be  driven  by  a 
belt  from  the  main  engine  or  shafting  or  by  an  electric  motor. 
The  independent  steam  driven  type  has  the  advantage  of  being 
absolutely  independent  of  the  main  engine;  it  may  be  started  be- 
fore and  stopped  after  the  main  engine,  thus  establishing  a  vac- 
uum before  the  load  is  thrown  on  the  engine  and  draining  the 
cylinder  and  pipes  of  the  water  of  condensation  and  leakage.     It 


Automatic   Vacuum  Bicakers  and  Relief  Valves.  31 

may  be  run  at  any  speed  within  its  limits,  keeping  the  vacuum 
constant  under  changes  of  load;  it  may  also  be  placed  at  any  con- 
venient point  near  the  engine.  On  the  other  hand,  it  is  more  ex- 
pensive to  operate  than  the  belt  or  electrically  driven  type,  as  the 
latter  obtain  their  power  at  the  same  cost  per  horse-power  as  that 
of  the  large  units.  We  will  not  discuss  here  the  relative  econ- 
omy of  the  different  types.  Another  point  of  importance  is  the 
possibility  of  damage  or  inconvenience  through  the  failure  of  the 
condensing  apparatus  or  the  improper  arrangement  of  the  con- 
necting pipes.  In  case  the  air  pump  fails  to  operate  or  the  in- 
jection pipe  becomes  clogged,  the  engine  must  be  shut  down  un- 
less it  is  provided  with  another  passage  for  the  exhaust.  The 
usual  method  is  to  provide  an  atmospheric  exhaust  outlet,  which 
will  allow  the  engine  to  exhaust  into  the  atmosphere.  As  shown 
in  Fig.  3,  this  outlet  is  provided  with  an  automatic  relief  valve  A. 
This  is  so  arranged  that  when  there  is  a  vacuum  in  the  exhaust 
pipe  between  the  engine  and  condenser  the  atmospheric  pressure 
on  the  outer  side  of  the  valve  keeps  it  closed.  If  the  air  pump 
becomes  inoperative,  the  pressure  accumulates  in  the  exhaust 
pipe  and  condenser  and  forces  the  valve  open,  allowing  the  engine 
to  exhaust  freely  into  the  atmosphere.  When  the  vacuum  is  re- 
established and  the  inside  pressure  falls  below  that  of  the  atmos- 
phere, the  valve  closes  automatically.  This  valve  may  be  a 
special  swing  check  or  any  one  of  a  number  of  other  special 
valves  made  for  the  purpose.  The  gate  valve  B  is  intended  for 
use  in  case  of  repairs  to  the  condenser;  it  may  be  closed  tightly 
and  the  automatic  valve  A  locked  open,  when  the  condenser  or 
air  pump  may  be  repaired  without  interference  from  the  hot  ex- 
haust steam.  In  case  the  condenser  and  air  pump  are  connected 
to  injection  and  discharge  mains  common  to  other  condensers  the 
gate  valves  C  and  D  are  necessary  in  the  event  of  repairs  to  the 
condenser  or  pump;  the  valve  C  is,  however,  primarily  intended 
to  regulate  the  supply  of  injection  water  as  will  be  mentioned 
later. 

Another  source  of  trouble  in  jet  condensing  engines  is  the  pos- 
sibility of  getting  water  into  the  engine  cylinder  and  so  wrecking 
it.  Suppose  the  air  pump  to  be  running  but  slowly,  or  to  stop 
entirely,  so  that  it  will  not  draw  out  the  injection  water  as  fast  as 
it  runs  into  the  condenser.     Eventually  the  water  will  flood  the 


32 


Types  of  Vacuum  Breakers. 


condenser  and  pipes,  enter  the  cylinder  and  wreck  it.  To  render 
this  impossible,  two  methods  are  adopted:  one  is  the  application 
of  a  vacuum-breaking  device  to  the  condenser;  the  other  is  to  so 
arrange  the  spray  cone  and  condenser  neck  that  an  accumulation 
of  water  will  reduce  the  surface  of  the  spray  and  break  the  vac- 
uum. 

Fig.  4  shows  a  patented  vacuum-breaker  furnished  on  all  Geo. 
F.  Blake  &  Knowles'  condensers.  Its  action  will  be  understood 
from  the  cut.  When  the 
water  rises  in  the  condenser 
to  the  level  AB,  it  lifts  the 
float  F,  which  in  turn  lifts 
the  air  valve  V  from  its 
seat,  admitting  air  to  the 
exhaust  pipe  and  engine 
cylinder  through  the  pipe 
P,  thus  breaking  the  vac- 
uum. This,  of  course, 
equalizes  the  inside  and 
outside  pressures,  and  pre- 
vents any  more  water  from 
flowing  into  the  condenser. 
The  engine  exhaust  will 
then  accumulate  until  it 
acquires  sufficient  pressure 
to  lift  the  valve  A,  Fig.  3, 
and  the  engine  will  ex- 
haust into  the  atmosphere. 

Fig.  5  shows  the  arrange- 
ment of  condenser  neck  and 
spray  cone  used  upon  the 
Worthington  condensers  to 
accomplish  the  same  result. 
In  this  case  the  water  is  sprayed  downward,  and  as  the  con- 
denser neck  is  quite  small,  the  rapid  condensation  is  due  only 
to  the  large  surface  exposed  by  the  spraying  water.  Owing 
10  the  small  size  of  the  condenser,  any  accumulation  of  water  rap- 
idly diminishes  the  condensing  surface  until  the  spray  itself  is 
submerged,  leaving  only  the  small  annular  ring  of  water  at  A  B 


How  to  Start  and  Stop  a  Condensing  Engine. 


33 


. 

2^- 

EXHAUST 
STEAM 

7     /I 

^_\%-~S( 

-B 

3 RAY  CONE 

to  act  on  the  large  volume  of  steam  from  the  engine.  The  sur- 
face of  this  ring  is  far  too  small  to  condense  the  steam  and  the 
pressure  immediately  accumulates  and  either  the  valve  A,  Fig. 
3  opens,  allowing  the  engine  to  run  non-condensing  or  the  ex- 
haust steam  blows  out  through  the  injection  pipe  and  pump 
valves. 

Again,  the  engine  itself  may  draw  water  up  into  the  low  pres- 
sure cylinder.  Suppose  a  compound  engine  having  a  low  pres- 
sure cylinder  of  4  times  the  area  of  the  high  pressure.  In  start- 
ing up  or  shutting  down  the  engine 
the  throttle  is  barely  cracked,  as 
usual,  admitting  throttled  steam  of, 
say,  20  pounds  absolute  pressure 
for  the  full  stroke.  At  the  end  of 
the  stroke  this  seam  will  be  admit- 
ted to  the  low  pressure  cylinder, 
where  it  expands  to  4  times  its 
volume,  or  to  about  5  pounds  ab- 
solute pressure.  This  is  equivalent 
to  a  vacuum  of  about  20  inches. 
Now  suppose  the  air  pump  to  be 
almost  or  entirely  stopped  and  the 
injection  valve  to  be  open  as  usual. 
Then  when  the  low  pressure  piston 
starts  on  its  return  stroke,  the  ex- 
haust valve  opens,  connecting  the 
cylinder  under  20  inches  of  vacuum 
with  the  exhaust  pipe  and  conden- 
ser, also  under  a  vacuum;  the  at- 
/w.jv.r.  mospheric    pressure  will   continue 

to  force  water  up  into  the  condenser,  and,  if  the  air  pump 
cannot  remove  it,  up  into  the  engine  cylinder.  This  would  be 
prevented  by  the  vacuum-breaking  device  shown  in  Fig.  4. 
This  brings  us  to  the  proper  method  of  starting  and  stopping  an 
engine  with  an  independent  condensing  apparatus.  To  start  the 
apparatus,  proceed  as  follows:  Open  slightly  the  injection  valve 
C  and  start  up  the  air  pump  to  its  normal  speed.  This  produces 
a  vacuum  in  the  pipes  and  condenser,  drains  them  of  all  water, 
and  causes  the  injection  water  to  flow  into  the  condenser.     When 


Fig.  5 


HYi 


34  Starting  a  Balking  hijection. 

the  vacuum  is  established,  as  shown  by  the  gage,  open  the  throt- 
tle and  turn  the  engine  over  slowly,  warming  it  up.  Then  bring 
the  engine  up  to  speed,  throw  on  the  load  and  regulate  the 
amount  of  injection  water  by  the  valve  C.  The  wheel  on  the 
top  of  the  condenser  is  used  only  for  regulating  the  thickness  of 
the  spray  and  has  nothing  to  do  with  the  supply  of  injection 
water. 

The  speed  of  the  air  pump  and  the  amount  of  injection  water 
must  be  regulated  according  to  the  load  on  the  engine  and  the 
amount  of  vacuum  desired. 

When  several  condensers  are  connected  to  a  common  injection 
main,  it  sometimes  happens  that  starting  up  the  air  pump  of  an  idle 
condenser  will  fail  to  bring  water  in  through  the  injection  branch. 
This  is  partly  owing  to  the  fact  that  the  greater  vacuum  already 
established  in  the  other  condenser  draws  the  water  away  from  the 
condenser  in  question,  but  in  a  greater  measure  it  is  due  to  the  fact 
that  a  flow  of  water  at  a  high  velocity  is  aheady  established  to  the 
other  condensers.  This  stream  of  water  requires  some  force  to 
break  its  flow  and  to  divert  a  portion  of  it  into  a  branch  pipe,  just 
as  the  stream  of  water  from  a  hose  nozzle  will  remain  a  smooth 
rod  of  water  for  some  distance  from  the  end  of  the  nozzle,  or  just 
as  the  jet  of  water  into  an  injector  tube  passes  the  spills  or  over- 
flow holes  without  losing  a  drop  of  water  through  them. 

In  such  event,  recourse  must  be  had  to  the  forced  injection  or 
priming  pipe  shown  in  Fig.  3.  This  forced  injection  takes  its 
supply  from  a  source  under  a  very  slight  head  or  pressure,  such 
as  a  surge  tank  slightly  elevated  or  the  city  water  supply.  If  the 
water  will  not  come  to  the  condenser, allow  the  air  pump  to  run, close 
main  injection  valve  C,  open  fully  priming  valve  E,  and  admit 
water  until  a  vacuum  is  formed  in  the  condenser;  then  open  gradu- 
ally injection  valve  Cand  close  priming  valve  E  gradually,  when 
it  will  be  found  that  the  flow  of  water  to  the  condenser  is  estab- 
lished. When  this  forced  injection  does  not  overcome 
the  trouble  entirely,  it  will  usually  be  found  that  the  injection 
pipes  are  too  small,  making  the  velocity  of  flow  too  great.  In 
such  cases,  the  velocity  of  flow  should  be  decreased  by  increasing 
the  size  of  the  injection  main  and  branches. 

When  shutting  down  an  engine  with  an  independent   condens- 


Stopping  an  ungine  with  an  Independent  Condenser.         35 

ing  apparatus,  close  the  engine  throttle  first,  and  when  the  engine 
has  stopped,  and  not  until  then,  close  the  injection  valve  C,  and 
lastly  shut  down  the  air  pump.  By  shutting  off  the  water  supply 
before  the  air  pump  is  stopped,  the  water  already  in  the  con- 
denser and  pipes  is  pumped  entirely  out  and  there  is  no  danger  of 
it  getting  into  the  engine  cylinder. 


THE  SURFACE  CONDENSER. 


Suppose  that  we  have  a  cylindrical  vessel  arranged  as  in  Fig. 
6,  with  a  pipe  through  the  center,  leaving  an  annular  space  out- 
side of  the  pipe.  If  we  fill  the  annular  space  with  steam  and  run 
a  stream  of  cold  water  through  the  pipe,  the  steam  will  condense 
upon  the  cold  pipe  surface  and  fall  to  the  bottom  of  the  vessel, 
leaving  a  vacuum  above  it.     If  we  draw  off  this  condensed  steam 

and  the  air  it  brought  in 
with  it,  we  can  refill  the 
vessel  with  steam  and,  by 
running  more  cold  water 
through  the  pipe,  condense 
this  new  steam;  this  opera- 
tion can  be  continued  in- 
definitely and  a  constant 
vacuum  maintained  in  the 
vessel.  In  this  case,  we  see 
that  the  exhauster  draws 
out  only  the  condensed 
steam  and  entrained  air, 
the  cooling  water  being 
kept  entirely  separate. 

In  the  jet  condensing  arrangement  shown  in  Figs,  i  and  2,  it 
is  plain  that  the  condensing  water  flows  into  the  vessel  on  account 
of  the  vacuum  therein;  while  in  this  case  the  part  of  the  vessel 
which  is  under  a  vacuum  is,  as  we  said  above,  entirely  separate 
from  the  condensing  water,  making  it  necessary  to  force  the  water 
through  the  pipe  by  some  other  means 

This  is  exactly  the  manner  in  which  the  surface  condenser 
operates. 

Fig.  7  shows  a  sectional  view  of  a  complete  surface  condenser 
and  pumps. 


o 


Power.  N.T. 


37 


38  Description  of  Surface  Condenser. 

The  exhaust  steam  from  the  engine  enters  the  condenser 
through  the  elbow  on  top;  it  then  expands  and  fills  the  space  out- 
side of  and  between  the  condenser  tubes.  The  circulating  pump 
shown  at  the  left  draws  its  water  by  "suction"  from  any  con- 
venient source  and  circulates  it  through  the  tubes,  keeping  them 
cold.  The  exhaust  steam  is  condensed  by  contact  with  these  cold 
surfaces  and  falls  to  the  bottom  of  the  condenser.  It  is  then 
drawn  off  by  the  air  pump  shown  at  the  right,  and  is  usually  dis- 
charged into  a  hot  well.  The  drawing  shows  clearly  that  the 
condensed  steam,  being  outside  the  tubes,  is  kept  entirely  separate 
from  the  condensing  water,  which  is  forced  through,  the  tubes. 
Evidently  then,  the  condensed  steam  discharged  by  the  air  pump 
may  be  used  over  again  in  the  boilers,  even  if  the  cooling  water  is 
unfit  for  use,  the  only  objection  to  this  being  the  oil  brought  down 
by  it  from  the  engine  cylinder  and  steam  chest.  There  are  several 
more  or  less  satisfactory  methods  of  extracting  this  oil  or  grease 
from  the  water;  a  discussion  of  their  merits  is  beyond  the  province 
of  this  article.  The  condensing  water  is  handled  by  a  separate 
pump  and  does  not  flow  into  the  condenser,  as  in  the  case  of  a  jet- 
condensing  apparatus;  it  may  be  salt  or  impure,  and  unless  warm 
water  is  required  for  some  outside  purpose  it  is  discharged  to 
waste. 

It  is  thus  seen  that  a  surface  condensing  apparatus  requires  two 
pumps  of  comparatively  small  size  as  against  one  large  pump  for 
the  jet  condenser.  It  is  considerably  more  expensive  than  the 
latter,  and  is  seldom  used  except  where  it  is  desirable  to  return 
the  condensed  steam  to  the  boilers. 

The  possibilities  of  trouble  from  it  are  less  than  in  the  jet  con- 
denser. There  is  no  way  in  which  the  condensing  water  can  get 
into  the  engine  cylinder;  while  the  condensed  steam  might,  under 
certain  conditions  of  air  pump  operation,  accumulate  until  it 
reached  the  top  of  the  condenser,  it  could  not  get  into  the 
cylinder,  for  the  condensing  surface  would  be  entirely  submerged 
and  the  accumulated  pressure  would  force  open  the  automatic  at- 
mospheric relief  valve  and  allow  the  engine  to  exhaust  into  the 
atmosphere. 

There  is  the  same  need  of  an  atmospheric  exhaust  outlet  as  in 
the  case  of  the  jet  condenser  and  for  precisely  the   same   reason. 

The  piping  between  the  engine,  the  elbow  on  the  condenser,  and 


Types  of  Air  Pumps. 


39 


the  atmospheric  exhaust  should  be  the  same  as  in  Fig.  3.  In  (he 
type  of  apparatus  shown,  the  condenser  is  directly  attached  to  the 
pump  or  pumps.  This  is  not  at  all  necessary;  the  air  or  circulat- 
ing pump  or  both  may  be  placed  at  any  convenient  point  and  con- 
nected with  the  condenser  by  pipes.  The  air  pump,  however, 
should  be  placed  below  the  condenser,  so  that  the  condensed  steam 
may  go  to  it  by  gravity.  Nor  is  it  necessary  to  use  the  type  of 
pump  shown  by  the  drawings.  The  pumps  may  be  horizontal  or 
vertical;  of  the  single  or  double-acting  single- cylinder  type;  the 
single-acting  twin-cylinder  type;  or  the  duplex  type.  Fig.  8 
shows  a  horizontal  double-acting  cylinder  air  pump,  independently 


£=0 


Fig.  8. 

steam-driven,  which  is  frequently  used  with  both  jet  and  surface 
condensers.  The  condenser  outlet  is  connected  with  the  suction 
inlet  of  the  pump,  and  its  operation  is  the  same  as  any  double-act- 
ing pump. 

Centrifugal  pumps  are  frequently  used  as  circulating  pumps, 
and  various  combinations  of  pumps  and  condensers  are  made. 

Fig.  9  shows  a  surface  condenser  equipped  with  3-cylinder  ver- 
tical reciprocating  air  pumps  and  centrifugal  circulating  pumps, 
both  pumps  being  driven  by  electric  motors.  The  details  of  the 
condenser  itself  vary:  for  instance,  a  jet  condenser  is  frequently 
box-shaped  instead  of  bottle  or  cone-shaped  as  in  Fig.  3;  a  sur- 
face condenser  may  be  rectangular  in  cross  section  instead  of 
cylindrical,  as  in  Fig.  7;  the  steam  may  be  inside  and  the  water 
outside  the  tubes  of  a  surface  condenser,  instead  of  as  shown  in 
Fig.  7;  etc.,  etc.     The  principle  is  the  same,    however,  in  all  ar- 


4o 


Motor- Driven  Air  and  Circulating  Pumps. 


rangements;  in  a  jet -condensing  apparatus  the  steam  is  condensed 
by  contact  with  a  jet  or  spray  of  cold  water  and  the  air  pump 
handles  the  condensed  steam,  the  condensing  water  and  the  air 
entrained  in  both;  in  a  surface  condensing  apparatus  the  steam  is 
condensed  by  contact  with  a  cold  surface  and  the  air  pump  handles 


EXHAUST  INLET 


the  condensed  steam  and  the   air,   while    the    circulating   pump 
handles  the  condensing  or  circulating  water  alone. 


THE  INJECTOR  OR  SIPHON  CONDENSER. 


Fig.  10  is  a  small  ^cale  reproduction  of  the  jet  condensing  ap- 
paratus described  in  Fig.  3.  It  will  be  seen  that  with  the  arrang- 
ments  shown,  an  air  pump  is  required  to  pump  out  the  condensed 
steam,  the  condensing  water  and  the  air  brought  in  by  both. 

If  the  hot  well  were  lowered  to  a  point  about  34  feet  below  the 
condenser,  as  shown  by  the 
dotted  lines,  it  will  be  seen 
that  an  air  pump  is  not  re- 
quired to  remove  the  con- 
densed steam  and  the  water. 
This  will  be  plain  if  it  is 
remembered  that  a  perfect 
vacuum  of  30  inches  in  the 
engine  exhaust  pipe  will 
not  support  a  column  of 
water  in  the  discharge  pipe 
more  than  34  feet  high;  so 
that  if  any  water  is  sup- 
plied to  the  condenser  in 
excess  of  this  34- foot  col- 
umn it  will  pass  through 
the  condenser  and  out  of  the 
discharge  pipe  without  the  aid  of  a  pump.  Now,  if  the  neck  of 
the  condenser  be  contracted,  as  in  Fig.  11,  the  velocity  of  this 
falling  water  will  be  greatly  increased,  and  the  water  will  carry 
out  with  it  not  only  the  condensed  steam  but  the  air,  leaving  a 
vacuum  in  the  exhaust  pipe. 

This  is  the  principle  of  the  injector  or  siphon  condenser,  one 
type  of  which,  the  Bulkley,  is  shown  in  cross-section  in  Fig.  12. 
As  will  be  seen  from  the   figure,  it  is  not  necessary  to  place  the 


42 


Principle  of  Injector  Condenser. 


O 


O 


o 


o 


£ 


condenser  below  the  engine,  as  in  Figs.  10  and  n.  All  that  is 
required  is  to  have  the  column  of  water  between  the  condenser  and 
the  hot  well  as  great  or  greater  than  the  vacuum  will  support,  so 
that  the  constant  supply  of  condensing  water  will  produce  a  con- 
tinuous downward  flow.  In  the  arrangement  shown  the  hot  well 
is  a  little  below  and  the  condenser  is  above,  the  engine  level,  an 
ordinary  tank  pump  being  used  to  elevate  the  condensing  water. 
The  exhaust  steam  enters  the  top  of  the  condenser  and  passes 
through  the  inner  cone  or  nozzle  C.     The  condensing  water  enters 

the  condenser  at  the  side  and 
passes  downward  around  the  ex- 
haust nozzle  in  a  thin  conical 
film.  The  exhaust  steam  is  con- 
densed within  this  hollow  cone  of 
falling  water,  and  the  condensed 
steam  and  the  condensing  water 
then  fall  vertically  through  the 
condenser,  and  discharge  pipe. 
In  passing  through  the  neck  of 
the  condenser  the  water  acquires 
sufficient  velocity  to  draw  out 
with  it  the  entrained  air,  leaving 
a  vacuum  in  the  exhaust  pipe 
and  engine  cylinder.  The  lower 
end  of  the  discharge  pipe  is 
sealed  by  the  water  in  the  hot 
well.  It  is  necessary  to  provide 
a  large  condensing  surface,  as 
well  as  a  high  velocity  for  the  in- 
jection water;  in  most  condensers 
of  this  type  this  is  provided  for  by 
bringing  the  exhaust  steam  in 
through  the  cone  or  nozzle  C,  and 
the  injection  water  in  through  the  annular  space  outside  the  cone. 
This  forces  the  condensing  water  to  take  the  shape  of  a  hollow 
cone  into  which  the  exhaust  steam  is  discharged. 

In  the  Knowles  Spirojector  condenser,  which  is  otherwise  simi- 
lar to  the  Bulkley,  the  cone  C  has  cast  on  its  face  vanes  which 
compel  the  injection  water  to  assume  a  spiral  or  whirling  motion 
as  it  passes  through  the  condenser  to  the  discharge. 


Fig.  11 


HOT    WELL 


Arrangement  of  Injector  Coridensor. 


43 


In  Fig.  12  a  pump  is  shown  for  lifting  the  condensing  water;  if 
the  level  of  the  injection  water  supply  is  not  more  than,  say,    20 

RELIEF  VALVE 


feet  below  the  condenser  inlet,  the  condenser  will  siphon  the  water 
over  as  soon  as  a  vacuum  is  formed  in  it  and  the  water  pump  may 


44 


The  Injection    Water  Supply. 


be  dispensed  with.  As  20  feet  is  about  the  limit  to  which  water 
may  be  continuously  lifted  by  the  siphoning  action,  it  follows 
that  when  the  water  supply  is  more  than  20  feet  below  the  con- 
denser a  pump  must  be  used.  The  arrangement  with  a  pump 
shown  in  Fig.  1 2  is  sometimes  modified  by  the  insertion  of  a  tank 
(shown  in  dotted  lines)  at  about  the  lower  limit  of  the  siphon. 
This  is  convenient  when  a  single-acting  or  single-cylinder  tank 
pump  is  used  to  lift  the  water;  such  a  pump  gives  a  more  or  less 
intermittent  flow,  whereas  a  practically  constant  flow  is  required 
by  the  condenser.  In  the  tank  arrangement,  the  pump  discharges 
intermittently  into  the  tank  and  the  condenser  siphons  continu- 
ously from  the  tank.  Fig. 
13  shows  the  arrangement 
of  condenser  and  pipes  for  a 
siphoning  apparatus,  when 
no  pump  is  used.  In  this 
figure  there  is  shown  a 
cross  connection  at  the  sup- 
ply level  between  the  injec- 
tion and  discharge  pipes. 
As  we  said  before,  the  vac- 
uum must  be  formed  in  the 
condenser  before  it  will 
siphon  water;  by  opening 
the  starting  valve  ^S  water 
is  admitted  to  the  discharge 
pipe,  and  in  falling  through 
the  pipe  it  draws  the  air  out 
with  it,  forming  enough 
vacuum  in  the  upper  pipes 
and  condenser  to  draft  the  injection  water  up  to  the  condenser.  The 
starting  valve  should  then  be  closed  and  the  water  supply  should 
be  regulated  by  valve  J.  When  the  injection  supply  is  at  the  ex- 
treme lower  limit  of  the  siphon,  say  20  feet  below  the  condenser, 
this  arrangement  of  starting  valve  is  not  always  satisfactory;  in 
such  cases  the  cross  connection  may  be  omitted  and  a  small  prim- 
ing pipe  P,  shown  in  dotted  lines  in  Fig.  13,  may  be  run  from  the 
boiler  feed  pump  discharge  to  the  condenser  inlet.  As  soon  as 
the  injection  water  appears  the  valve/  may  be  closed  and  the  feed 


Adva?itagcs  of  the  Type. 


45 


RELIEF  VALVE 


pump  may  resume  its  usual  duty.  When  a  pump  is  used  to  ele- 
vate the  water,  the  starting  valve  or  priming  pipe  and  the  injec- 
tion valve/  are  of  course  omitted,  as  the  vacuum  is  formed  by 
forcing  water  directly  into  the  condenser,  and  the  water  supply 
is  regulated  by  the  pump  speed. 

This  type  of  condenser  is  suitable  for  many  locations,  and  if 
properly  made  and  connected  will  maintain  a  good  vacuum.  It  is 
economical  in  operation  and  has  no  moving  parts  to  wear  or  to  get 
out  of  order.  There  is  no  way  in  which  water  can  get  into  the 
engine  cylinder  unless  it  is 
allowed  to  accumulate  in  the 
pocket  formed  by  the  ex- 
haust pipe,  and  not  even 
then  unless  atmospheric 
pressure  is  admitted  to  the 
exhaust  pipes  through  the 
uncovering  of  the  water 
supply  or  discharge  pipes. 
A  drain  pipe  placed  as 
shown  in  Fig.  12  will  serve 
to  drain  out  the  exhaust 
pipe  before  the  engine  is 
started  and  removes  all 
danger  from  this  source. 
Pumping  action  of  the  low 
pressure  cylinder  cannot 
draw  water  up  from  the  hot 
well  on  account  of  the 
height,  and  water  drawn 
up  from  the  injection  supply  would  fall  into  the  discharge  pipe 
and  not  into  the  exhaust  pipe,  by  reason  of  the  construction. 
Another  condenser  of  this  type,  but  differing  slightly  from  the 
above  in  detail,  is  the  Baragwanath  water  jacket  condenser  shown 
in  Fig.  14.  In  this  condenser,  as  in  the  others,  the  exhaust  en- 
ters at  the  top  and  the  injection  at  the  side,  and  the  exhaust  noz- 
zle is  surrounded  by  cold  water.  The  water  chamber  is  larger 
than  in  the  others,  and  the  shell  of  the  condenser  is  prolonged  in- 
side the  water  chamber,  forming  an  inverted  cone,  into  the  end  of 
which  the  condensing  nozzle  C projects.     This  nozzle  is  adjustable 


46  Automatic  Relief  Valve. 

by  means  of  the  spindle  shown  and  can  be  set  to   admit  precisely 
the  right  amount  of  water. 

Each  of  the  three  condensers  mentioned  herein,  i.  e.,  the  Bulk- 
ley  injector,  the  Knowles  Spirojector  and  the  Baragwanath  water 
jacket,  is  supplied  with  an  automatic  atmospheric  relief  valve 
similar  to  that  shown  in  Fig.  13;  this  valve  discharges  directly 
into  the  atmosphere,  so  that  when  the  top  of  the  condenser  is  in- 
side the  building  it  is  necessary  to  use  a  relief  valve  in  the  pipe 
line  and  to  carry  the  atmospheric  exhaust  pipe  out  of  doors.  This 
valve  may  be  of  the  swinging  check  type  shown  in  Fig.  3,  or  any 
one  of  several  well-known  types.  The  injection  water  may  be 
supplied  under  a  head  or  a  pump  of  either  the  reciprocating,  the 
rotary  or  the  centrifugal  type  may  be  used.  The  head  against 
which  these  pumps  work  is  evidently  quite  small,  since  the 
vacuum  in  the  condenser  will  take  care  of  the  upper  18  or  20 
feet  of  the  lift. 


THE  EXHAUST  STEAM  INDUCTION  CONDENSER. 


The  operation  of  this  condenser  is  based  upon  the  same  principle 
as  that  of  the  steam  injector.  As  most  of  our  readers  know,  the 
operation  of  the  injector  is  as  follows:  A  jet  of  steam  enters 
through  the  steam  tube  at  a  high  velocity  and  induces  the  air  in 
the  suction  pipe  and  injector  body  to  pass  out  with  it;  this  leaves 
a  vacuum  and  allows  the  atmospheric  pressure  to  force  in  water. 
The  steam  is  condensed  by  this  water  and  the  velocity  of  the 
steam  is  imparted  to  the  water;  then  the  energy  in  the  moving 
column  of  water  is  sufficient  to  overcome  the  pipe  friction,  lift 
the  check  valve  and  force  the  water  into  the  boiler  against  the 
pressure. 

An  inspection  of  Fig.  15  shows  that  this  is  exactly  the  opera- 
tion of  the  induction  condenser.  The  exhaust  steam  enters 
through  the  valve  E  and  passes  through  the  inclined  perforations 
into  the  central  tube  T,  as  shown  by  the  arrows.  Owing  to  the 
velocity  of  its  movement  the  air  in  the  condenser  and  the  injec- 
tion pipe  is  drawn  out  with  it,  and  the  atmospheric  pressure  on 
the  injection  supply  forces  the  condensing  water  up  through  the 
pipe  and  into  the  tube  T  as  shown.  The  exhaust  steam  is  con- 
densed by  this  water  and  a  vacuum  is  left  in  the  condenser 
and  exhaust  pipe.  The  original  velocity  with  which  the  water 
entered  the  condenser  and  the  added  velocity  due  to  the 
exhaust  steam  enable  the  mingled  steam  and  water  to  over- 
come the  atmospheric  pressure  on  the  discharge  end  and 
pass  out  into  the  hot  well,  just  as  the  water  from  the  injector 
overcomes  the  resistance  due  to  friction  and  pressure  and  passes 
into  the  boiler.  From  this  we  see  that  the  velocity  of  the  dis- 
charge is  sufficient  to  draw  out  the  air  and  to  get  rid  of  the  con- 
densing water  and  condensed  steam;  so  that  no  air  pump  is  re- 
quired as  in  the  case  of  a  jet  or  surface  condenser,  nor  a  34-foot 
"tail"  column,  as  in  the  injector  or  siphon  condenser. 


48 


Arrajigement  of  Induction   Co?ide?iser. 


The  condenser  shown  in  Fig.  15,  however,  has  its  limits  of 
operation.  We  have  just  seen  that  the  operation  depends  upon 
the  velocity  of  the  discharge;  it  is  plain  that  when  the  condenser 
lifts  its  injection  water,  as  shown  in  the  figure,  this  velocity  must  be 
almost  wholly  imparted  by  the  exhaust  steam.  Then  if  the  load 
on  the  engine  is  variable  or  if  the  condenser  is  too  large  for  the  en- 
gine, there  will  be  times  when  the  small  amount  of  exhaust  steam 


QHI 


Fig.  15. 


furnished  by  the  engine  will  not  be  enough  to  impart  the  required 
velocity  to  the  large  volume  of  water  and  the  condenser  will  not 
operate  satisfactorily.  In  other  words,  the  volume  of  exhaust 
steam  must  be,  within  limits,  in  proportion  to  the  volume  of 
water  which  it  keeps  in  motion,  too  little  steam  being  unable  to 
induce  the  flow  of  water  and  too  much  steam  affecting  the  vac- 
uum.    The  minimum  amount  is  that    which  will  increase  the 


Adjusting  the  Capacity. 


49 


temperature  of  the  water  at  least  300  F.  and  the  maximum 
amount  is  that  which  will  not  cause  a  rise  of  more  than  500  F.  in 
the  water  temperature. 

In  cases  where  the  condenser  takes  its  water  under  a  head,  as 
shown  by  dotted  lines  in  Fig.  15,  this  objection  does  not  apply, 
for  then  the  velocity  of  the  water  is  that  due  to  the  head  and  is 
independent  of  the  exhaust  steam. 

In  order  to  guard  against  the  trouble  due  to  a  varying  amount 
of  exhaust  steam,  the  con- 
denser shown  in  Fig.  16  has 
been  devised.  It  is  called 
the  adjustable  capacity  con- 
denser in  order  to  distin- 
guish it  from  the  fixed 
capacity  condenser  shown 
in  Fig.  15.  Both  the  con- 
densers shown  were  design- 
ed by  Korting  and  are 
identified  with  1^.  Schutte 
in  America. 

The  adjustable  condenser 
shown  in  Fig.  16  is  provid- 
ed with  a  movable  ram  R 
inside  the  central  water 
tube  and  a  sleeve  £  out- 
side the  tube.  The  ram  is 
tapering  and  controls  the 
volume  of  water  admitted 
by  increasing  or  diminish- 
ing the  annular  space  be-  ***,&* 
tween  its  surface  and  the  inside  of  the  tube;  while  the  sleeve  5, 
by  covering  more  or  fewer  openings  in  the  tube,  governs  the  area 
of  the  exhaust  inlet  and  consequently  the  velocity  of  the  exhaust 
steam.  The  relative  positions  of  the  ram  and  the  sleeve  can  be 
regulated  by  the  extension  rod  K,  so  that  the  machine  can  be 
adjusted  for  almost  any  condition  of  load.  In  fact,  the  machine 
may  be  adjusted  to  work  satisfactorily  at  any  point  from  j{  or 
1-5  of  its  capacity  to  full  capacity;  this  is  particularly  desirable, 


5<d  Preventing  Flooding. 

as  we  have  said,  when  the  load  is  variable  and  the  injection  water 
must  be  lifted.  On  the  other  hand,  the  range  of  the  fixed  ca- 
pacity condenser  is  only  from  about  one-half  capacity  to  full  ca- 
pacity. For  high  suction  lifts,  the  live  steam  jet  or  water  pres- 
sure jet/ is  used  to  bring  the  water  to  the  condenser,  and  an  es- 
cape is  provided  through  the  overflow  valve  O  just  as  in  the  case 
of  the  steam  injector.  This  starting  jet  and  overflow  valve  are 
necessary  only  when  starting,  and  may  both  be  omitted  when 
the  suction  lift  is  very  small  or  when  water  is  supplied  under  a 
head.  It  will  be  seen  that  in  this  condenser,  as  in  the  jet  and 
siphon  condensers  previously  described,  the  condensed  steam 
and  the  condensing  water  are  mixed  together,  so  that  the  water 
from  the  hot  well  can  not  be  used  for  boiler  feed  unless  the  con- 
densing water  is  pure.  An  inspection  of  Fig.  1 5  shows  that  an 
atmospheric  outlet  must  be  provided  for  the  exhaust,  just  as  in  the 
cases  of  the  jet,  surface  and  siphon  condensers.  The  figure  shows 
a  special  swing  check  valve  for  this  purpose,  while  on  the  adjust- 
able capacity  condenser  in  Fig.  16  is  shown  the  automatic  valve 
usually  furnished  with  this  type  of  condenser. 

In  this  condenser  there  is  no  34- foot  tail  column,  and  in  case 
the  low  pressure  cylinder  of  the  engine  acts  as  a  pump,  water  may 
readily  be  drawn  up  into  the  engine. 

This  is  prevented  by  the  arrangement  of  the  stop  valve  E, 
through  which  the  exhaust  steam  enters  the  condenser.  The 
valve  itself  is  not  fixed  to  the  spindle,  but  is  free  to  move  verti- 
cally within  the  limits  set  by  the  seat  at  the  bottom  and  the  collar 
C  on  the  spindle  at  the  top.  It  thus  allows  steam  to  pass  out 
under  it  from  the  engine  into  the  condenser,  but  acts  as  a  check 
valve  against  the  passage  of  water  in  the  opposite  direction  or 
from  the  condenser  to  the  engine.  It  may  also  be  used  as  a  stop 
valve  by  lowering  the  spindle  until  the  collar  C  locks  the  valve 
to  its  seat.  Since  the  seat  of  this  valve  is  practically  at  the  top 
of  the  exhaust  pipe,  it  is  advisable  to  drip  the  pipe  on  the  engine 
side  of  the  valve,  as  shown  in  Fig.  15,  to  prevent  any  accumula- 
tion of  condensation.  This  drip  may  be  piped  into  the  condenser 
as  shown,  with  a  check  valve  arranged  to  prevent  the  return  of 
water  from  the  condenser  to  the  exhaust  pipe. 

The  directions  for  starting  or  stopping  au  engine  equipped  with 
either  type   of   this   condenser   are   very   simple.     It  is   always 


Stopping  and  Starting  with  an  Induction   Condenser.       51 

desirable  to  start  the  condenser  and  form  the  vacuum  before 
starting  the  ermine,  as  we  have  mentioned  in  connection  with  the 
other  condensers. 

To  start  the  engine,  proceed  as  follows: 

When  the  condensing  water  is  under  a  head,  turn  on  the  con- 
densing water  and  when  a  vacuum  is  formed  start  up  the  engine. 
When  the  condensing  water  must  be  lifted,  open  the  steam  or 
pressure  jet  valve/,  and  as  soon  as  this  has  lifted  the  water  start 
the  engine.  The  operation  of  the  condenser  will  begin  as  soon  as 
the  engine  exhaust  reaches  the  condenser  and  when  the  vacuum 
is  formed  the  suction  or  lifting  jet  may  be  turned  off.  In  shutting 
down,  stop  the  engine  first,  when  the  operation  of  the  condenser 
will  cease  if  the  condensing  water  is  under  a  suction  lift;  if  the 
water  supply  is  under  a  head,  stop  the  engine  first  and  then  shut 
the  valve  in  the  water  supply  pipe. 


52 


CONDENSER  CAPACITIES. 


In  column  4  of  Table  I  are  given  the  number  of  heat  units 
required  to  raise  a  pound  of  water  from  zero  Fahrenheit  to  the 
corresponding  temperatures  T  in  column  3. 

In  column  5  are  given  the  numbers  of  so-called  '  'latent' '  heat 
units  L  required  to  convert  a  pound  of  water  at  the  corresponding 
temperatures  T  into  dry  saturated  steam  of  the  same  temperature, 
the  corresponding  pressures  being  given  in  various  units  in  columns 
1  and  2. 

Column  6  gives  the  total  number  of  heat  units  H  required  to 
raise  a  pound  of  water  from  zero  F.  to  the  corresponding  temper- 
ature and  to  convert  it  into  steam  of  that  temperature.  It  is  the 
sum  of  the  corresponding  values  in  columns  4  and  5. 

For  example,  in  a  vacuum  of  25  inches  (column  1),  wmich  is 
the  same  thing  as  an  absolute  pressure  of  2.417  pounds  to  the 
square  inch  (column  2),  water  vill  boil  at  133  degrees  F.  (column 
3).  It  will  take  133.21  heat  units  to  raise  a  pound  of  water  from 
zero  F.  to  this  temperature  (column  4),  and  1,021.295  more  heat 
units  (column  5)  to  evaporate  the  pound  at  that  pressure  and 
temperature,  making  a  total  of  1,154.505  (column  6). 

To  make  a  pound  of  steam  at  an  absolute  pressure  of  20  pounds 
(column  2)  from  a  pound  of  water  at  1  io°  would  require 

1,183.454—110.110  =  1,073.344 
heat  units,  because  the  pound  of  water  has  already  no.  no  heat 
units  in  it  (column  4)  above  what  it  would  have  at  zero  F. ,  and 
there  are  in  a  pound  of  steam  of  20  pounds  pressure  absolute 
1,183.454  heat  units  above  the  number  in  a  pound  of  water  at 
zero  (column  6). 

Condensation  is  the  reverse  of  evaporation.     If  we  wish   to 


TABLE  I 

i     a       I 


-PHYSICAL  PROPERTIES  OP  SFBAJI. 

3  14  15  I 


Heat  Required 

to  Convert  a  Pound  of  Water 

Pressure 

Temperature. 

at  Zero  F.  into  Steam. 

Vacuum 

To    Raise   the 

To  Conr<jrt  the 

„by 

Absolute. 

Temperature 

Water  at  the 

Total. 

Gage. 

to    tho  Boil- 

Boiling Point 

T 

ing  Point. 

into  Steam. 

Inches 

Lbs.  per 

h 

L 

H 

Mercury. 

.^q  in. 

Degrees  F. 

Heat  Units. 

Heat  Units. 

Heat  Units. 

29.74 

.089 

32 

32 

1091.700 

1123.700 

29.72 

.100 

35 

35 

1089.015 

1124.615 

29.  G7 

.122 

40 

40.001 

1086.139 

1126.140 

29.6  J 

.147 

45 

45.002 

1082.661 

1127.665 

29.56 

.170 

50 

50.003 

1079.187 

1129.190 

29.49 

.212 

55 

55.000 

1075.709 

1130.715 

29.40 

.254 

GO 

60.009 

1072.231 

1132.240 

19.30 

302 

65 

05.011 

1068.751 

1133.765 

29.19 

.359 

70 

70.020 

10G5.270 

1135.290 

29 

.425 

75 

75.027 

1061.788 

1136.815 

28.90 

.502 

80 

80.030 

1058.304 

1138.340 

28.72 

.590 

85 

85.045 

1054.8  0 

1139.&65 

28.51 

.692 

90 

90.055 

1051.355 

) 141. 390 

23.27 

.809 

95 

95.0G5 

1047.850 

1142.915 

28 

.943 

100 

100.080 

1044.300 

1144.440 

27  85 

1. 

102 

102.086 

1042.9C4 

1145.050 

27.09 

1.094 

105 

105.095 

1040.870 

1145.965 

27.34 

1.205 

110 

110.110 

1037.380 

1147.490 

27 

1.435 

114.34 

114.470 

1034.344 

1148.814 

26.95 

1.462 

115 

115.129 

1033.880 

1149.015 

26.50 

1.682 

120 

120.149 

1030.391 

1150. 54J 

26 

1.931 

125 

125.169 

1026.896 

1152.0b5 

25.85 

2. 

126.266 

126.440 

1026.010 

1152.450 

25.42 

2.213 

130 

130.192 

1023.389 

1153.590 

25 

2.417 

i:53 

133.21 

1021.295 

1154.505 

24.79 

2.520 

135 

135.217 

1019.898 

1155.115 

24.  GO 

2.876 

140 

140.245 

1016.305 

1156.640 

24 

2.9 

141.293 

141 .543 

1015.491 

1157.034 

23  81 

3. 

141.622 

141.877 

1015.254 

1157.131 

23  26 

3  270 

145 

145.275 

1012.890 

1153.165 

23 

3.399 

146.528 

146.808 

1011.823 

1158.631 

22  37 

3.707 

150 

150.305 

1009.385 

11:9.690 

22 

3.9 

152.0") 

152.37 

1007.945 

1160.315 

21  73 

4 

153.070 

153.396 

1007.229 

1160.625 

21  39 

4.' 191 

155 

155.339 

1005.876 

1161.215 

21 

4  373 

156.74 

157.09 

1004.452 

1161.542 

20.29 

4.729 

1G0 

160.374 

1002.366 

1162.740 

20 

4.S63 

]61.   63 

161.543 

1001.552 

1163.095 

19  74 

5. 

1G2.33 

162.722 

1000.727 

1103.449 

19  08 

5.324 

163 

105.413 

998.852 

1161.265 

19 

5.30 

105.317 

105.730 

998.632 

1164.362 

n 

5.855 

109 

169.45 

990.035 

1165.485 

17.74 

5.981 

170 

170.453 

9)5.337 

1165.790 

17.71 

c. 

170.123 

170.577 

995.249 

1165.826 

17 

6.346 

172.6 

173.07 

993.513 

1166.583 

lrf.27 

6.704 

175 

175  497 

991.818 

1167.315 

1G 

6.837 

175.9 

176.4 

991 . 180 

1167.580 

15  67 

7. 

176.910 

177.425 

990.471 

1167.896 

15 

7.329 

178.98 

179.51 

989.019 

1163.529 

14  65 

7.500 

180 

180.542 

988.298 

1168.840 

14 

7.82 

181.877 

182.427 

086.980 

1169.407 

13  63 

8. 

182.910 

183.481 

986.245 

1169.726 

13 

8.311 

184.668 

185.25 

985.014 

1170.204 

12  87 

8  :-75 

185 

185.591 

984.774 

1170.365 

ia 

8  802 

187.272 

187.885 

933.360 

1171.245 

11. GO 

9. 

183.316 

1S8.941 

932.434 

1171.375 

11 

9.293 

189.82 

190.46 

981.375 

1171.835 

10  92 

9.33 

190 

190.613 

981. 047 

1171.890 

10 

9.784 

192.21 

192.89 

979.674 

1172.561 

9.56 

10. 

193. *40 

193.919 

978.958 

1172.877 

0 

10.275 

194.53 

195.22 

978.052 

1173.272 

8.79 

10.33 

195 

195. 6&7 

977.713 

1173.415 

8 

10.767 

196.742 

197.46 

976.480 

1173.946 

7.53 

1.. 

197.768 

198.496 

075  762 

1174.258 

7 

11.253 

198  9 

199. C4 

974.964 

1174. 6"4 

6.46 

11.52 

200 

200.753 

974.167 

1 174  940 

54 


Heat  in  a  Pound  of  Steam. 


6 

r  n.7 

6.49 

12. 

5 

12.24 

4 

12.73 

3.93 

12.766 

3.45 

13. 

3 

13.222 

2 

13.714 

1.42 

14. 

1.17 

14.122 

1 

14.205 

14.G96 

Gage 

Pressure 

lbs.  per 

gq. inch. 

.304 

15 

1.304 

1<S 

2.304 

17 

3.304 

18 

4.304 

19 

6.304 

20 

6.304 

21 

7.304 

22 

8.801 

23 

9.304 

24 

10.304 

25 

11.304 

26 

12.304 

27 

13.304 

28 

14.304 

29 

15.3J4 

30 

200.747 

201.514 

973.654 

1175.168 

201.960 

202.737 

972.800 

1175.537 

202.924 

203.712 

972.120 

1175.832 

'204.772 

205.58 

970.815 

1176.395 

£05 

205.813 

970.652 

1176.465 

205.88-) 

206.109 

970.025 

1176.734 

206.722 

207.557 

969.453 

1176.99 

208.522 

209.377 

968.162 

1177.539 

209.560 

210.428 

967.427 

1177.855 

210 

210.874 

967. 11G 

1177.990 

210.3 

211.17 

966.9115 

1178.0815 

212 

212.900 

965. 7C0 

1178.600 

213.025 

213.939 

9G4  973 

1178.912 

216.296 

217.252 

962.657 

1179  909 

219.410 

2C0.409 

D60.450 

1180.859 

222.378 

223.419 

958.345 

1181.764 

225.203 

226.285 

956.343 

1 182 . 628 

227.917 

229.0  9 

954.4  5 

1183.454 

230.515 

231.676 

952.570 

1184.246 

233.017 

234.218 

950.791 

1185.009 

235.432 

236.672 

949.072 

1185.744 

237.752 

239.029 

947.424 

1186.453 

240.000 

241.314 

945.825 

1187.139 

242.175 

243.526 

944.277 

1187.803 

244.281 

245.671 

942.775 

1188.446 

246  326 

247.748 

941.321 

1189.069 

248.310 

249.769 

9^9.905 

1189.674 

250.245 

251.738 

838.925 

1190.263 

reduce  a  pound  of  steam  at  an  absolute  pressure  of  20  pounds  to 
water  at  1  io°  we  shall  have  to  take  out  of  it 

1,183.554—110.110=  1,073.344 
heat  units,  because  the  pound  of   steam  contains  1,183.454  units, 
of  which  1 10  1 10  will  remain  in  the  water,  always  reckoning  from 
zero  Fahrenheit. 

It  will  be  seen  by  comparing  columns  3  and  4  that  the  heat  in 
the  water  is  very  nearly  the  same  as  the  temperature  of  the  water, 
the  increase  on  account  of  the  greater  specific  heat  at  higher 
temperatures  being  less  than  one  heat  unit  between  32 °  and  2120. 
It  will  be  sufficiently  accurate  for  our  purpose  to  consider  the 
heat  in  the  water  the  same  as  the  temperature,  i.  e.}  to  consider 
column  4  equal  to  column  3,  letting  a  heat  unit  represent  the 
amount  of  heat  necessary  to  raise  a  pound  of  water  one  degree 
irrespective  of  the  temperature. 

If  we  represent  by  t  the  temperature  at  which  the  injection  or 
circulating  water  comes  to  the  condenser  and  by  T  the  tempera- 
ture at  which  it  leaves,  the  number  of  heat  units  absorbed  by 
each  pound  will  be  approximately 

T—t. 

The  number  of  heat  units  to  be  taken  out  of  a  pound  of  steam 
to  condense  it  is,  as  we  have  seen  above, 

H—h, 


Water  Required  to  Condense  a  Pou?id  of  Steam.  55 

i.  e. ,  the  total  heat  in  the  steam  less  the  heat  in  the   resulting 
water. 

By  dividing  the  number  of  heat  units  to  be  abstracted  by  the 
number  absorbed  by  each  pound  of  condensing  water  we  find 
the  quantity,  Q,  of  water  required  to  condense  a  pound  of  steam 

Where  H  =  the   total   heat  in  a  pound  of  steam  of   the   given 
pressure, 
h  =  the  heat  in  a  pound  of  water  at  the  temperature  of 

the  condensed  steam, 
t=  the   temperature   at   which    the    condensing   water 
enters  the  cor  denser, 
T=  the   temperature   at  which    the    condensing    water 
leaves  the  condenser. 

TO  FIND  THE  AMOUNT  OF  WATER    REQUIRED    TO    CONDENSE   ONE 
POUND  OF  STEAM. 

Rule: — From  the  total  heat  in  one  pound  of  steam  of  the  given 
pressure  subtract  the  heat  i?i  one  pound  of  water  at  the  condenser 
temperature.  Divide  the  remainder  by  the  rise  in  temperature  of 
the  injection  or  circulating  water  in  passing  through  the  condenser. 
The  quotient  will  be  the  number  of  pounds  of  water  required  to  con- 
dense one  pound  of  steam. 

In  considering  the  condensation  of  steam  in  an  engine  the  value 
of  H  must  be  taken  at  the  terminal  pressure.,  not  at  the  counter- 
pressure  or  vacuum  line.  The  engine  delivers  the  steam  to  the 
condenser  at  the  pressure  existing  at  the  point  of  release,  and  if 
the  steam  were  dry  saturated  each  pound  would  carry  to  the 
condenser  the  number  of  heat  units  given  in  column  6  of  Table  I. 
There  is,  however,  little  difference  in  this  value  for  the  entire 
range  of  terminal  pressures  met  with  in  good  practice,  and  the 
quality  of  the  steam  may  vary  widely.  There  is  little  use  strain- 
ing after  extreme  accuracy  in  this  particular,  and  we  shall  be 
entirely  safe  for  the  average  case  and  not  far  from  right  in  any 
case  if  we  assign  to  H  the  maximum  probable  value  of  1,190, 
corresponding  closely  to  a  terminal  pressure  of  30  pounds  absolute. 

Call  the  temperature  of  the  air  pump  discharge  r,  which,  allow- 
ing one  heat  unit  per  degree  of  temperature,  would  equal  h. 

Substituting  these  values  for  H  and  h  in  formula  1  we  have 


56 


To  Find  Quantity  of  Water  Required 


1 1 90  —  T 
T—t 


(2) 


APPROXIMATE  RULE  FOR  THE  QUANTITY  OF  CONDENSING  WATER 
REQUIRED  PER  POUND  OF  STEAM  CONDENSED. 

Rule: — Subtract  the  temperature  of  the  air  pump  discharge  from 
1, 1  go  and  divide  the  remainder  by  the  rise  in  temperature  of  the 
condensi?ig  water. 

Table  II  has  been  computed  by  this  formula  and  gives  the 
values  of  Q,  i.  e. ,  the  pounds  of  water  required  to  condense  a 
pound  of  steam  for  condenser  temperatures  of  from  90  to  130  and 
with  from  5  to  90  degrees  of  difference  in  the  condensing  water. 

In  a  jet  condenser  where  the  condensing  water  is  mingled  with 

TABLE  II.— POUNDS  OF  WATER  REQUIRED  TO  CONDENSE   ONE  POUND  OF  STEAM. 

1190—  r 
Q  = 


T 

-t 

T-t 

Temperature  of  air  pump  discharge. 

r 

90 

95 

100 

102 

104 

106 

108 

110 

112 

114 

116 

118    j 

120   | 

125 

130 

5 

220 

219 

218 

217.6 

217.2 

216.8 

216  4 

216 

215.6 

215.2 

214.8 

214.4 

214 

213 

212 

10 

110 

109.5 

109 

108.8 

108.6 

108.4 

108.2 

108 

107.8 

107. 6 

107.4 

107.2 

107 

106.5 

106 

15 

73.3 

73 

72.7 

72.5 

72.4 

72.3 

72.1 

72 

71.9 

71.7 

71.6 

71.5 

71. 31 

71 

70.7 

20 

55 

54.7 

54.5 

54.4 

54.3 

54.2 

54.1 

54 

5J.9 

53.8 

53.7 

53.6 

53.5 

53.2 

53 

25 

44 

43.8 

43.  . 

43.5 

43.4 

43.4 

43.3 

43.2 

43.1 

43 

42.9 

42.9 

42.8) 

42.6 

42.4 

30 

36.7 

36.5 

36.3 

36.3 

,c6.2 

36.2 

36.1 

36 

35.9 

35.9 

35.8 

35.7 

35.7 

35.5 

35.3 

3) 

31.4 

31.3 

31.1 

31.1 

31.0 

31 

30.9 

30.8 

30.8 

30.7 

•  0.7 

30.6 

30.5 

30.4 

30? 

40 

27.5 

27.4 

27.2 

27.2 

27.1 

27.1 

'27 

27 

26.9 

26.9 

26.8 

'26.8 

26.7 

26.6 

26.5 

45 

24.4 

24.3 

24.2 

24.2 

24.1 

24.1 

24 

24 

23.9 

23.9 

23.9 

23.8 

23.8 

23.7 

23  5 

50 

22 

21.9 

21.8 

21.8 

21.7 

21.7 

21.6 

21.6 

21.6 

21.5 

21.5 

21.4 

21.4 

21.3 

21.2 

55 

20 

19.9 

19.8 

19.8 

19.7 

19.7 

19.7 

19.6 

19.6 

19.6 

19.5 

19. 5j 

19.4 

19.4 

19.  S 

60 

18.3 

18.2 

18.2 

18.1 

18.1 

18.1 

18 

18 

18 

17.9 

17.9 

17  9 

17.8 

17.7 

17  7 

G5 

16.9 

16.8 

16.8 

16.7 

16.7 

16.7 

16.6 

16.6 

16.6 

16.5 

16.5 

16.5 

16.5 

16.4 

16.3 

70 

15.7 

15.6 

15.6 

15.5 

15.5 

15.5 

15.4 

15.4 

15.4 

15.4 

15.3 

15.3 

15.3! 

15.2 

15.1 

75 

14.7 

14.6 

14.5 

14.5 

14.5 

14.4 

14.4 

14.4 

11.4 

14  3 

14.3 

14.3 

14.3! 

14.2 

14.1 

80 

13.7 

13.6 

13,6 

13,6 

13,6 

13.5 

13.5 

13.5 

13.5 

13.4 

13.4 

13  4 

13.41 

13.3 

13.2 

85 

12,9 

12.8 

12.8 

12,8 

12,8 

12.7 

12.7 

12.7 

12  7 

12.6 

12.6 

12.6 

12.6 

12.5 

12.5 

90 

12  2 

12.2 

12.1 

12.1 

12.1 

19 

12 

12 

12 

11.9 

11.9 

11.9 

11.9 

11.8 

11.8 

the  steam  T  and  r  become  identical  and  formula  becomes 

a  —  IT9°—  T 

V  T—t 

Table  III  has  been  computed  by  this  formula  and  gives  the 
value  of  Q,  i.  e.,  the  number  of  pounds  of  injection  water  required 
per  pound  of  steam  with  the  injection  water  from  35  to  100 
degrees  and  the  air  pump  discharge  from  900  to  1400. 

SIZE  OF  AIR  PUMP  FOR  JET  CONDENSER. 

If  we  designate  by  H^the  weight  of  steam  to  be  condensed  per 
hour,  the  number  of  pounds  of  water  to  be  handled  per  hour  by 
the  pump  will  be 

W(Q+i). 


Displacement  Required  for   Water. 


0/ 


For  example,  if  we  had  a  ioo  horse  power  engine  using  20 
pounds  of  steam  per  hour  per  horse  power  the  weight  JVoi  steam 
to  be  condensed  per  hour  would  be  20 X  100=  2,000  pounds.  If 
it  takes  20  pounds  of  water  to  condense  a  pound  of  steam,  then 
for  each  pound  of  steam  condensed  we  shall  have 

20 -f-  1  pounds 
of  water  to  pump,  20  pounds  of  injection  and  one  pound  of  con- 
densed steam.     For  2,000  pounds  we  shall  have 
W  (g-f  1)  =  2,000(20+  1). 

XARLE  III. 


a, 
®  *  2 

£  3(1| 

E-t  °  w 


92 
91 
96 
98 
100 
102 
104 
106 
108 
110 
112 
114 
116 
118 
120 
122 
124 
126 
128 
130 
132 
134 
136 
138 
140 


-POUNDS  OF  INJECTION   WATER  .REQUIRED  PER  POUND  OF 
STEAM  CONDENSED. 

Entering  Temperature  of  Injection  Water  t. 


3j         40         45         50         55         GO         65         70         75 


90       95      100 

I  I 


Pound.3  of  Condensing  Water  Required  per  Pound  of  Steam.     Q  = 


1190—  T 
T—t 


20  0 
19.2 
18  6 
17.9 
17  3 
16.8 
16.2 
15.7 
15.3 
14.8 
14.4 
14.0 
13.6 
13.3 
12.9 
12.6 
12.3 
12.0 
11.7 
11.4 
11.2 
10.9 
10.7 
10.4 
10.2 
10.0 


»0 

24.4 

21.1 

23.4 

20  3 

22.4 

19.5 

21.4 

18.8 

20.6 

18.2 

19.8 

17.5 

19.1 

17.0 

18.4 

16.4 

17.8 

15.9 

17.2 

15.4 

16.6 

15.0 

16.1 

14  5 

15.6 

14.1 

15.1 

13.7 

14.7 

13.4 

14.3 

13.0 

13.9 

12.7 

13.5 

12.4 

13.1 

12.1 

12.8 

11.8 

12.5 

11.5 

12.2 

11.2 

11.9 

11.0 

11.6 

10.7 

11.3 

10.5 

11.1 

27.5 
26.1 
24  9 
23.6 
22.7 
21.8 
20.9 
20.1 
19.4 
18.7 
18.0 
17.4 
16.8 
16.3 
15.8 
15.3 
14.8 
14.4 
14.0 
13.6 
13.2 
12.9 
12.6 
12.3 
12.0 
11.7 


31.4 

36.7 

29.7 

34.3 

28.1 

32.2 

26.7 

30.4 

25  4 

28  7 

24.2 

27.2 

23.1 

25.9 

21.2 

24.7 

21.3 

23.6 

20.4 

22.5 

19.6 

21.6 

18.9 

20.7 

18.2 

19  9 

17.6 

19.2 

17.0 

18.5 

16.5 

17.8 

15.9 

IT. 2 

15.4 

16.7 

15.0 

16.1 

14.5 

15.6 

14.1 

15.1 

13.7 

14.7 

13  4 

14.3 

13.0 

13.9 

12.7 

13.5 

12  4 

13.1 

44.0 

40.7 
37.8 
35.3 
30.1 
31.1 
29.4 
27.8 
26.4 
25.2 
24.0 
22.9 
42.0 
21.1 
20.2 
19.5 
18.7 
18.1 
17.4 
16  9 
16.3 
15.7 
15.3 
14.8 
14.4 
14.0 


55.0 
49.9 
45.7 
42.1 
39.0 
36.3 
34.0 
31.9 
30.1 
28.5 
27.0 
25.7 
24.5 
23.3 
22.3 
21.4 
20.5 
19.7 
19.0 
18  3 
17.7 
17.1 
16.5 
16.0 
15.5 
15.0 


73  3 
64.6 
57.7 
52.1 
47.5 
43.6 
40.3 
37.4 
35.0 
32.8 
30.9 
29.1 
27.6 
26.2 
24.9 
23.8 
22.7 
21.8 
20.9 
20.0 
19.3 
18.6 
17.9 
17.3 
16.7 
16.2 


110.0 
91.5 
78  1 
68.4 
60.7 
54.5 
49.5 
45.2 
41.7 
38.6 
36.0 
33.6 
31.6 
29.8 
28.2 
26.7 
25.4 
24.2 
23.1 
22.1 
21.2 
20.3 
19.6 
IS. 8 
18.1 
17.5 


220.0 
156.8 
121.8 
99.4 
84.0 
72.7 
64.0 
57.2 
51.6 
47.0 
43.2 
39.9 
37.1 
34.6 
32.5 
30.6 
28.9 
27.3 
26.0 
24.7 
23.6 
22  5 
21.6 
20.7 
19.8 
19.1 


549.0 
274  .-0 
182.3 
136.5 
109.0 
90.7 
77.6 
G7.7 
G0.1 
51.0 
49.0 
44.8 
41.3 
38  3 
35.7 
33.4 
31.4 
29.6 
27.9 
26.5 
25.2 
24.0 
22.9 
21.9 
21.0 


364.0 
218.0 
155.4 
120.7 
98.5 
83.2 
72.0 
63  4 
56.6 
51.1 
46.6 
42.8 
39.6 
36.8 
34.3 
32.2 
30.3 
28.6 
27.1 
25.7 
24.5 
23.3 


544.0 
271.5 

180.7 
135.2 
1084) 
89.8 
76.9 
67.1 
59.6 
53.5 
48.5 
44.4 
40.9 
37.9 
35.3 
33.1 
31.0 
29.2 
27.7 
26.2 


It  takes  in  round  numbers  28  cubic  inches  to  make  a  pound  of 
water  at  ordinary  condenser  temperatures,  so  that  if  we  multiply 
this  by  28  we  shall  get  the  number  of  cubic  inches  of  water  to  be 
pumped  per  hour.  By  dividing  this  by  60  we  get  the  number  of 
cubic  inches  to  be  pumped  per  minute,  and  our  formula  so  far 
becomes 
Water  pumped  per  minute= 

28 
W  (04-  1)  ^-cubic  incheSc 
v  60 


58  Additional  Displacement  for  Air. 

But  in  addition  to  the  water  we  have  a  considerable  quantity  of 
air  to  handle,  and  we  cannot  count  upon  an  efficiency  of  ioo  per 
cent,  so  we  must  provide  a  pump  of  a  displacement  considerably 
more  than  the  volume  of  the  water.  I,et  us  call  the  ratio  of  the 
pump  displacement  to  the  volume  of  the  water  R.  For  instance, 
if  the  displacement  were  twice  the  volume  of  the  water  or  the 
pump  were  allowed  to  half  fill  with  water,  R  would  be  2.  Then 
the  pump  displacement  D  in  cubic  inches  per  minute  would  be 

If  there  is  any  standard  value  for  R,  if  we  can  determine  what 
proportion  of  their  displacement  it  is  safe  or  advisable  to  allow 
pumps  of  the  different  types  to  fill,  we  can  combine  this  standard 

28 

value  of  R  with  the  fraction  ~^~  into  a  coefficient  K  and  the 
formula  becomes 

D  =  KW{Q+i).  (3) 

For  instance  suppose  it  was  the  usual  practice  to  use  a  pump 
having  a  displacement  of  twice  the  volume  of  the  water  to  be 
pumped,  i.  e.,  to  let  the  pump  fill  half  full  of  water,  then  R 
Vould  equal  2,  and 

60  60  ^ 

andZ)=.93  W(Q+i). 

Table  IV  gives  the  values  of  K  for  various  values  of  R.  If 
the  pump  fills  with  water  to  60  per  cent,  of  its  displacement 
(column  1),  i.  e.y  if  the  displacement  is  1.667  times  the  volume 
of  the  water  (column  2),  the  value  of  A'wouldbe  .78  (column  3). 

In  order  to  establish  the  values  of  K  used  in  current  practice 
with  various  kinds  of  pumps  we  have  obtained  from  such  manu- 
facturers as  were  willing  to  furnish  them  the  data  contained  in 
Tables  V  to  XIII.  From  the  data  in  columns  2  to  6  the  displace- 
ment D  in  cubic  inches  per  minute  has  been  computed,  corrected 
for  the  rod,  when  its  diameter  (column  3)  was  known.  Columns 
9  and  10  give  the  value  of  Wy  i.  e.}  the  weight  of  steam  con- 
densed per  hour  which  the  pump  is  adapted  to  take  care  of  by  the 
builder's  rating.  The  values  in  column  10  are  all  reduced  to  20 
pounds  of  injection  water  to  1  of  steam.  When  the  builder's 
rating  is  based  upon  a  different  value  of  Q  it  is  to  be  found  in 
column  8.     In  columns  13  and  14  are  the  values  of  A"  correspond- 


To  Find  Size  of  Air    Pump, 


59 


ing  with  the  ratings  for  jet  and  surface  condensers  respectively. 

Take,  for  example,  the  Conover  vertical  single  acting  air  pump, 
Table  V.  For  a  jet  condenser  the  value  of  K  for  everything  but 
the  smallest  size  is  .75  (column  13).  In  column  n  is  given  the 
capacity  computed  by  the  formula  as  given  at  the  head  of  the 
column,  which  is  simply  a  transposition  of  formula  3,  taking  K 
= .  75  and  the  values 
there  given  will  be  seen 
to  run  very  close  to  the 
builder's  rating. 

Knowing  the  value  of 
K  the  process  becomes 
very  simple.  Suppose 
we  have  a  500  horse 
power  engine  using  20 
pounds  of  steam  per  hour 
per  horse  power;  that 
the  temperature  of  the 
injection  water  will  be 
for  considerable  periods 
as  high  as  65  °,  and  we 
want  to  keep  the  hot  well 
or  condenser  temperature 
down  to  no°.  What 
size  Conover  pump 
should  we  require  ?  We 
see  from  Table  III  that 
it  will  take  24  pounds  of 
injection  water  per  pound 
of  steam;  then 

Q=    24; 

jv=  500  x  20  =  10,- 
000; 


TABLE  IV. -VALUES  OF  K    FOR 

DIFFERENT 

RATIOS  OF  DISPLACEMENT  TO  VOLUME 

OF 

WATER  HANDLED 

1 

2 

3 

Per  cent  of  Air 

Ratio  of  Air 

Pump  Dis- 

Pump Displace- 

Value 

placement  Filled 

ment  to  Volume 

of 

with  Water. 

of  Water. 

K. 

V 

D 

28 

100  — 

R  =  — 

K  =  -R 

D 

V 

60 
Surface. 

5 

20 

9.33 

5.26 

19 

8.87 

5.56 

18 

8.40 

5.88 

17 

8.00 

6.26 

16 

7.47 

6.66 

15 

7 

7.14 

14 

6.P3 

7.69 

13 

6.07 

8.33 

12 

5.60 

9.09 

11 

6.13 

10.00 

10 

4.67 
Jet. 

33.33 

3 

1.4 

35 

2.941 

1.33 

36 

2.778 

1.30 

38 

2.632 

1.23 

40 

2.5 

1.17 

42 

2.381 

1.11 

44 

2.273  . 

1.07 

46 

2.174 

1.02 

47 

2.143 

1 

48 

2.083 

.97 

50 

2 

.93 

52 

1.923 

.90 

54 

1.852 

.86 

56 

1.786 

.83 

58 

1.724 

.80 

60 

1.667 

.78 

62 

1.613 

.75 

64 

1.5*2 

.73 

66 

1.515 

.71 

66.67 

1.5 

.70 

68 

1.471 

.69 

70 

1.429 

.67 

72 

1.389 

.65 

74 

1.351 

.63 

75 

1.333 

.62 

76 

1.316 

.61 

78 

1.282 

.GO 

80 

1  250 

.58 

75; 


K 

and 

D=  K  W  (Q  -f-  1)  =  .75  X  10,000  X  25  =  187,500  cu.    in. 
per  min. 

The  sizes  nearest  to  this  capacity  are  the  numbers   1 1   and  1 2 


60  To  Find  Size  of  Air  Pump. 

(which,  by  the  way,  have  the  same  size  of  air  cylinder  but  differ- 
ent steam  cylinders),  having  a  capacity  of  158,340,  and  the 
numbers  13  and  14,  with  a  capacity  of  204,781  cubic  inches  per 
minute.  The  purchaser  can  determine  if  it  is  safe  in  his  case  to 
take  the  next  smaller  or  whether  the  next  larger  is  necessary. 

For  the  double-acting  horizontal  pumps  the  value  of  K  runs 
very  close  to  unity  in  several  of  the  tables,  although  some  of  the 
makers  rate  them  so  high  as  to  bring  K  down  to  a  figure  which 
gives  them  a  considerably  greater  efficiency  than  the  vertical 
single-acting  pumps.  What  incongruities  there  are  in  the  columns 
of  K  are  evidently  due  to  erratic  ratings,  for  there  should  be  no 
reason  why  one  pump  of  the  same  kind  and  make  should  have  a 
greater  displacement  per  pound  of  water  handled  than  the  size 
next  to  it,  saving  always  that  very  small  sizes  may  be  less  efficient 
than  the  larger.  Where  the  diameter  of  the  rod  is  not  given 
there  would  be  a  greater  proportional  difference  between  the  net 
and  gross  displacement  in  the  smaller  sizes,  which  would  call  for 
a  larger  value  of  K  for  a  very  small  pump  where  the  displace- 
ment is  uncorrected  for  the  rod.  As  for  the  difference  in  the 
values  of  K  as  given  by  the  ratings  of  the  different  makers  we 
must  leave  our  readers  to  judge  whether  there  should  be  so  much 
difference  in  the  efficiency  of  the  respective  pumps  that  one  could 
be  allowed  to  fill  over  78  per  cent. ,  while  the  other  fills  less  than 
50  per  cent,  of  the  stroke. 

From  the  data  presented  the  conclusion  would  appear  warranted 
that  a  safe  value  for  K  would  be  .75  for  vertical  single-acting 
pumps  and  unity  for  horizontal  double-acting  pumps,  and  that 
pumps  selected  by  the  following  formulas  would  be  very  close  to 
what  the  makers  would  recommend  for  the  capacity  required: 

For  horizontal  double- acting  pumps: — 

D=  W(Q+t)  (4) 

For  vertical  singlk-acting  pumps: — 

Z>=.75  1V(Q+i)  (5) 

to  determine  the  size  of  air  pump  required  for  a  jet 

condenser. 

RULE: — Multiply  the  number  of  pounds  of  steam  to  be  condensed 
per  hour  by  one  plus  the  number  of  pounds  of  injection  water  ?r- 
quired  per  pound  of  steam.      The  product  will  be  the  required  pump 


How  Pumps  Should  be  Rated.  6r 

displacement  in  cubic  indies  per  minute  for  a  horizontal  double- 
acting  pump.  For  a  single-acting  vertical  pump  multiply  the 
above  product  by  .75. 

In  column  1 1  of  the  tables  are  given  the  capacities  calculated 
by  formula  4  or  5,  according  to  the  type  of  pump.  In  all  except- 
ing a  few  instances  of  abnormally  high  rating  the  capacities  will 
be  seen  to  agree  substantially  with  the  rated  capacities  of  the 
builders  in  column  9. 

We  are  informed  by  one  of  the  makers  that  they  find  the  long 
rating  perfectly  safe,  because  they  always  use  the  size  next  above 
the  required'  computed  capacity.  For  instance,  Dean  Bros,  rate 
their  7X  I2  X  I2  at  5,535  pounds  of  steam  per  hour,  with  26 
pounds  of  injection  to  one  of  steam,  which  gives  a  value  for  K  of 
.632.  This  requires  the  pump  to  fill  with  water  to  almost  74  per 
cent,  of  its  volume  (Table  IV),  a  condition  which  could  not  be 
counted  upon  to  preserve  a  good  vacuum  with  a  double-acting 
horizontal  pump,  but  this  pump  is  used  for  everything  between 
2,300  and  5,500.  With  a  capacity  of  about  2,950  its  coefficient 
becomes  unity  and  its  capacity  ample.  Much  of  the  time,  too, 
the  temperature  of  the  injection  would  be  such  that  less  than  26 
pounds  of  injection  would  be  used,  and  it  is  improbable  that  the 
maximum  conditions  of  load  and  injection  temperature  will  come 
together.  On  a  pinch,  too,  the  speed  of  the  pump  could  be 
increased  above  that  given  in  columns  5  and  6.  We  think,  how- 
ever, that  the  pump  should  be  rated  at  what  it  will  do  continu- 
ously and  comfortably  under  the  given  conditions,  and  the 
engineer  be  allowed  to  decide  how  much  he  wishes  to  exceed  that 
capacity  in  the  maximum  demand  which  he  is  likely  to  put  upon 
it.  The  reduction  of  the  ratings  to  a  common  unit  of  K=  1  for 
horizontal  double-acting  pumps  and  K=  .75  for  single-acting 
vertical  pumps  (column  11)  makes  this  possible  and  easy.  It 
should  be  noticed  that  this  column  is  computed  for  20  pounds  of 
injection  to  one  of  steam. 

In  selecting  a  pump,  it  should  be  remembered  that  the  work 
done  depends  upon  the  volume  of  air  and  water  delivered  against 
the  atmospheric  pressure,  and  not  upon  the  size  of  the  pump.  In 
Fig.  4,  which  is  a  section  of  the  Conover  single-acting  pump, 
suppose  the  volume  of  air  and  water  in  the  chamber  B  to  be  so 
small  that  the  air  would  not  be  compressed  enough  to  lift  the  head 


62 


Work  Performed  by  Air  Pump. 


valves.  On  the  upward  stroke  the  pump  performs  the  work  of 
lifting  the  water  resting  on  the  piston  and  of  compressing  the  air. 
On  the  downward  stroke  the  water,  in  descending,  gives  back 
the  work  required  to  lift  it,  and  the  air  in  expanding  the  work 
required  to  compress  it,  so  that  no  work  is  done  except  that 
required  to  overcome  friction.  When  the  volume  of  air  and  water 
in  B  becomes  so  great  that  the  head  valves  are  lifted  the  remainder 
of  the  stroke  is  completed  against  the  pressure  of  the  atmosphere, 
and  the  work  done  is  proportional  to  the  volume  of  air  and  water 


Fig.  4. 

delivered  at  atmospheric  pressure.  Aside,  then,  from  the 
additional  investment  in  and  friction  of  the  larger  pump,  it  is  at 
no  disadvantage  over  the  smaller. 

In  computing  the  displacement  of  a  single-acting  pump,  it 
should  be  noted  that  when  a  foot- valve  is  used,  the  pump  is  to 
an  extent  double  acting.     This  will  be  seen  by  reference  to  Figs. 


Single  Acting  Pump  with  Foot  Valve  is  Double  Acti?ig.     63 

2  and  3.  When  the  piston  is  in  its  highest  position,  as  in  Fig.  2, 
we  have  the  volume  between  the  head  and  the  foot  valves  con- 
taining only  the  piston.  When  the  piston  is  in  its  lowest  position 
(Fig.  3)  this  volume  has  been  further  reduced  by  the  volume  of 
the  trunk,  and  a  volume  equal  to  the  cross  sectional  area  of  the 
trunk,    multiplied    by    the 

length  of  the  stroke,  must  I   Fig  2  Fig. 3. 

have        been       discharged  i||||| 

through  the  head  valves  on 
the  downward  stroke. 
When  the  area  of  the  trunk 
becomes  equal  to  that  of 
the  annular  space  around  it, 
the  pump  discharges  as 
much  on  the  downward  as 
upon  the  upward  stroke.  Where  no  foot-valve  is  used,  as  in 
Fig.  1,  the  water  is  held  against  the  piston  by  the  head  at  Ay 
avoiding  the  disagreeable  chug  which  occurs  when  the  piston  is 
allowed  to  come  against  a  confined  body  of  water. 

The  factor  of  uncertainty  in  air  pump  work  is  the  air  entering 

by      leakage.      This      air 
entering  at  the  atmospheric 
pressure  of.  say,  15  pounds, 
I  expands  in  a  vacuum  of  26 
I  inches  to  over  7    times  its 
£  original  volume,    and   this 
I  increased  volume   must  be 
I  provided  for  in  the  displace- 
3  ment  of  the    air  cylinder. 
This  factor  is  therefore  an 
exceedingly  important  one, 
4   and  is  very  variable.  Some 
plants  are  tight,  others  are 


no  eixT«F 


BY  ICflK/VGE 


JNDENSING    WATER 


-2O-V0LuMtS- 


£4  VOLUMES 


5<>   W.JLUME 


Fig. 


not.  Generally  plants  using  a  small  amount  of  steam  per  horse 
power  have  a  large  leakage  factor,  because  while  the  amount  of 
steam  used  per  horse  power  is  decreased,  the  leakage  is  liable  to 
go  the  other  way,  the  pressure  in  the  lower  pressure  cylinder  be- 
ing much  of  the  time  below  that  of  the  atmosphere. 


64  Size  of  Air    Pump  for  Surface    Condenser. 

SIZE  OF  AIR  PUMP  FOR  SURFACE  CONDENSER. 

In  a  jet  condenser,  the  air  pump  has  to  handle  a  comparatively 
large  amount  of  water.  In  the  surface  condenser  it  handles  a 
small  volume  of  water  and  a  large  volume  of  air.  Assume  20 
pounds  of  injeccion  to  one  of  steam  condensed,  air  carried  by  the 
water  one- third  the  volume  of  the  water  when  expanded,  and  an 
air  pump  with  a  displacement  about  two  and  a  half  times  the 
volume  of  the  water  to  be  moved.  Under  these  conditions  we 
should  have  in  Fig.  1 : 

At  A  the  condensed  steam  =  1  vol. 

At  B  the  condensing  water  =  20  vols. 

At  Cthe  air  entering  with  the  water  =  7  vols. 

And  at  D  the  space  which  it  is  found  necessary  to  provide  for 
the  air  entering  by  leakage  and  to  cover  the  deficiencies  of  the 
pump,  consisting  of  24  volumes. 

In  a  surface  condenser  we  have  to  handle  only  the  water 
represented  by  A.  The  space  B,  therefore,  can  be  cut  out  of  the 
diagram,  as  can  also  the  space  C,  as  the  only  water  which  can 
bring  in  air  is  the  comparatively  small  quantity  used  for  make-up. 
We  are  liable  to  have  as  much  air  enter  by  leakage  into  a  surface 
as  into  a  jet  system,  so  that  the  portion  of  the  space  D  which  is 
required  for  air  entering  by  leakage,  and  this  is  the  greater  por- 
tion of  it,  will  remain  unchanged.  The  portion  required  to  cover 
the  lack  of  perfection  in  the  pump  will  diminish  with  the  volume 
pumped.  With  a  pump  of  half  the  size  a  less  number  of  cubic 
inches  of  volume  will  be  lost  by  failure  to  fill,  slippage,  failure  of 
valves  to  seat,  etc. 

If  D  were  left  as  it  is,  we  should  have  a  displacement  25  times 
the  volume  of  the  water  pumped.  The  practice  of  the  pump 
companies  generally  is  to  give  the  air  pump  a  displacement  equal 
to  20  times  the  volume  of  the  condensed  steam,  if  it  is  a  horizontal 
double-acting,  and  1 2  times  if  it  is  vertical  single-acting.  The 
Conover  company  give  their  pumps  a  displacement  of  only  10 
times  the  volume  of  the  condensed  steam. 

The  values  of  A"  for  these  ratios  are: 
R  K 

10     =     4.67 
12     =     5.6 
20     =     9-33 


Air  Pump  for  Surface  Condenser.  65 

For  general  use  these  values  may  safely  be  taken  at  9  for  a 
horizontal   double-acting,  and  at  5  for  a   vertical   single-acting 
pump.     Since  there  is  no  injection  the  volume  of  water  to  be 
handled  is  simply  W,  and  the  formulas  become: 
For  a  horizontal  double-acting  pump 

D  =  9W  (6) 

For  a  vertical  single-acting  pump 

B  =  5W  (7) 

or  generally 

D  =  KW  (8) 

TO    DETERMINE    THE    SIZE    OF    AIR    PUMP    REQUIRED    FOR  A  SURFACE 

CONDENSER. 

Multiply  the  number  of  pounds  of  steam  to  be  condensed  per  hour 
by  9  for  a  horizontal  double-acting  or  by  5  for  a  vertical  single- 
acting  pump.  The  product  will  be  the  air  pump  displacement 
required  in  cubic  inches  per  minute. 

In  column  1 2  of  the  tables  are  given  the  capacities  calculated 
by  formula  6  or  7,  according  to  the  type  of  pump.  A  comparison 
between  columns  10  and  12  will  show  how  nearly  the  formula 
with  the  constants  chosen  will  come  to  the  builder's  rating.  Of 
course  the  general  formula  8  may  be  employed,  the  user  choosing 
his  own  value  of  K. 

CONDENSING  SURFACE   REQUIRED. 

In  the  early  days  of  the  surface  condenser  it  was  thought 
necessary  to  provide  a  cooling  surface  in  the  condenser  equal  to 
the  heating  surface  in  the  boilers,  the  idea  being  that  it  would 
take  as  much  surface  to  transfer  the  heat  from  a  pound  of  steam 
to  the  cooling  water  and  condense  the  steam  as  it  would  to 
transfer  the  heat  from  the  hot  gases  to  the  water  in  the  boiler  and 
convert  it  to  steam.  The  difference  in  temperature,  too,  between 
the  hot  gases  and  the  water  in  the  boiler  is  considerably  greater 
than  that  between  the  steam  in  the  condenser  and  the  cooling 
water.  Steam,  however,  gives  up  its  heat  to  a  relatively  cool 
surface  much  more  readily  than  do  the  hot  furnace  gases,  and  the 
positively  circulated  cooling  water  takes  up  that  heat  and  keeps 
the  temperature  of  the  surfaces  down,  while  in  a  boiler  the 
absorption  depends  in  a  great  measure  upon  the  ability  of  the 
water  by  natural  circulation  to  get  into  contact  with  the  surface 


66  Cooling  Surface  in  Surface  Condensers. 

and  take  up  the  heat  by  evaporization.  It  has  been  found,  there- 
fore, that  a  much  smaller  surface  will  suffice  in  a  condenser  than 
in  the  boilers  which  it  serves. 

The  Wheeler  Condenser  and  Engineering  Company,  who  make 
a  specialty  of  surface  condensers,  say  that  one  square  foot  of 
cooling  surface  is  usually  allowed  to  each  10  pounds  of  steam  to 
be  condensed  per  hour,  with  the  condensing  water  at  a  normal 
temperature  not  exceeding  75  °.  This  figure  seems  to  be  gener- 
ally used  for  average  conditions.  Special  cases  require  special 
treatment.  For  service  in  the  tropics  the  heating  surface  should 
be  at  least  ten  per  cent,  greater  than  this  estimate:  Where  there 
is  an  abundance  of  circulating  water  the  surface  may  be  much 
less,  as  with  a  keel  condenser,  where  50  pounds  of  steam  is  some- 
times condensed  per  hour  per  square  foot  of  surface;  or  a  water 
works  engine,  where  all  the  water  pumped  is  discharged  through 
the  condenser  and  not  appreciably  raised  in  temperature,  probably 
condensing  20  to  40  pounds  per  hour  per  square  foot  of  surface. 

Mr.  J.  M.  Whitham,  in  a  paper  upon  "Surface  Condensers," 
presented  to  the  American  Society  of  Mechanical  Engineers,* 
gives  the  following  formula  for  calculating  the  surface  required: 

C—  WL 

180  (  T—.t) 

Where 
S-=  the  surface  in  square  feet, 
W=  the  weight  of  steam  condensed  per  hour, 
L  =  the  latent  heat  of  steam  at  the  condenser  temperature, 
T=  the  temperature  of  the  condenser,  or  the  air  pump  dis- 
charge, 
and  /  =  the  average  temperature  of  the  circulating  water,  i.  e. ,  the 
sum  of  its  initial  and  final  temperatures,  divided  by  2. 
For  ordinary  conditions  this  reduces  to 

o      17   W 

*~    180 

or  one  square  foot  of  heating  surface  to  about  10.6  pounds  of  steam 
condensed  per  hour. 

This  refers  to  the  ordinary  arrangement  of  horizontal  brass 
tubes  of  small  diameter  to  the  surface  condenser  as  ordinarily 

*See  Trans.  A   S.  M.  E.,  Vol.  IX,  p,  417. 


Size  of  Injectiori  Main.  67 

used.     With   other  arrangements  of  surface,  etc.,  it  might  not 
apply. 

CONDENSING   WATER    PER   HORSE   POWER   IN   GALLONS. 

The  value  of  Q  can  be  reduced  to  gallons  by  dividing  by  8.25, 
for  since  one  pound  equals   28    cubic   inches   one   pound  equals 

2M=^250fagall0n- 

If  we  let  S  =  the  steam  required  per  horse  power  per  hour,  the 
weight  of  steam  to  be  condensed  per  hour  for  a  given  engine  will  be 

W=/fPXS 
The  condensing  water  required  in  pounds  per  hour  will  be 
WQ  =  //PXQXS 
in  gallons  per  hour, 

JfPXQXS 
8.25 
or,  in  gallons  per  minute, 

HPXQXS  ^HPXQXS 

60X8.25  495 

0  s 

This  is         gallons  per  minute  per  horse  power. 

Taking  20  pounds  of  steam  per  horse  power  per  hour  and  25 
pounds  of  condensing  water  per  pound  of  steam  the  condensing 
water  per  horse  power  = 

— — ass  - —  gals,  per  min., 

495  495 

or  just  about  a  gallon  per  minute  per  horse  power,  which  is  a 
a  much  used  value. 

SIZE  OF  INJECTION  MAIN. 

The  injection  main  should  be  so  proportioned  that  the  velocity 
of  flow  does  not  exceed  300  feet  per  minute,  a  velocity  which  will 
be  closely  approximated  by  making  the  diameter  of  the  pipe  the 
square  root  of  the  quotient  of  the  pounds  of  condensing  water 
required  per  hour  divided  by  6,000. 

For  examp1e.  to  condense  2,000  pounds  of  steam  per  hour  with 
24  pounds  of  injection  per  pound  of  steam  would  require 
24  X  2,000  =  48,000  pounds  of  injection  water  per  hour. 

Divide  this  by  6,000  and  extract  the  square  root  and  you  have 
the  pipe  diameter, 

48,000  -f-  6,000  =  8 


68  Relation  of  Temperature  and  Vacuum 

The  pipe  should  evidently  be  3  inches,   the  square  of  2.5,  the 
next  lower  size  being  6.25. 

If  there  were  no  air  present  in  the  condenser  the  temperature 
for  a  given  vacuum  or  absolute  pressure  would  be  that  given  in 
Table  1.  There  is  in  the  condenser,  however,  the  pressure  not 
only  of  the  steam  arising  from  the  water,  but  that  of  the  enclosed 
air,  so  that  for  a  given  condenser  temperature  the  absolute 
pressure  will  be  higher,  i.  e. ,  the  vacuum  will  be  less  than  in- 
dicated by  the  table.  With  a  temperature  of  air  pump  discharge 
of  1200,  for  instance,  we  should  have,  if  there  were  nothing  pres- 
ent but  the  water  and  the  steam  arising  from  it,  an  absolute 
pressure  of  1.682  pounds  per  square  inch,  or  a  vacuum  of  26.5 
inches.  We  cannot  have  a  lower  absolute  pressure,  i.  e.y  a  better 
vacuum,  with  this  temperature,  because  the  water  at  this  temper- 
ature will  continue  to  give  off  steam  of  this  pressure  and  keep  the 
condenser  full  of  it,  no  matter  how  much  capacity  wre  have  to  our 
air  pump.  Now,  if  we  admit  a  little  air  we  shall  have  an 
additional  pressure  with  no  increase  of  temperature,  and  of  course 
there  will  be  some  air  present.  For  this  reason  it  is  common  to 
see  condensers  running  with  a  discharge  temperature  of  ioo°, 
which  by  the  table  should  give  a  vacuum  of  over  28  inches,  with 
the  gage  showing  26  or  less. 


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78 


INDEX. 


B 


/\bsolute  Pressure,  9. 

Air  and  Circulating  Pumps  driven  by 
motors,  40. 

Air-Pump  for  Surface  Condenser,  65. 

Air-Pump  ;  location  of,  27. 

Air-Pump  rating,  61. 

Air-Pump  ;  To  find  size  of,  59-60. 

Air-Pump ;  Total  work  of,  62. 

Air- Pump  ;  Types  of,  39. 

Air-Pump  Valves  ;  lifting  or  clattering  of, 
27. 

Air-Pump  ;  Vertical,  22. 

Air;  Pumping,  10. 

Area  of  Cooling  Surface  in  Surface  Con- 
denser, 65-66. 

Atmosphere  ;  Pressure  of  the,  3. 

arr  Horizontal  Double-Acting  Pumps ; 
Table  of,  77. 

Capacity  of  a  Condenser ;  To  calculate 
the,  65-68. 

Circulating  Pump,  39-40. 

Cooling  Surface  of  a  Surface  Condenser, 
65-66. 

Cooling  Towers,  26 

Cooling  Water  required  for  condensing, 
15.  16,  55-57,  67. 

Condensation  in  a  Cylinder,  18-19 

Condensation  ;  Production  of  a  vacuum  by 
means  of,  11. 

Condenser  Capacity,  52-68 

Condenser ;  Induction  See  Induction  Con- 
denser. 

Condenser;  Injector.  See  Injector  Con- 
denser , 

Condenser  ;  Jet.    See  Jet  Condenser 

Condenser;  Siphon  See  Injector  Con- 
denser, 

Condenser;  Surface  See  Surface  Con- 
denser 

Condenser  unavailable,  17 

Condensers ;  Independent  and  direct- 
driven,  21. 

Condensing  by  Evaporation,  26. 

Condensing  Engine  ;  How  to  start  and  stop 
a,  33.  35,  5i- 


Condensing;  Gain  due  to,  12-14. 

Condensing ,  L,oss  in  temperature  of  feed- 
water  due  to,  14. 

Condensing ;  Water  required  for,  15,  16, 
55-57.  67 

Condensing  Water  per  Horsepower,  in 
gallons,  67. 

Condensing    Water ;    Pump    displacement 

required  for,  57. 
Conover    Vertical     Single-Acting     Pumps ; 

Table  of,  69. 
Cylinder  Condensation,  18-19. 

^J  iagram  of  Maximum  Efficiency,  20. 

Dean  Bros.'  Horizontal  Double-Acting 
Pumps,  Table  of,  70. 

Dean  Bros. '  Twin  Cylinder  Vertical  Single- 
Acting  Pumps  ;  Table  of,  76. 

Deane  Horizontal  Double-Acting  Pumps ; 
Table  of,  75. 

^^fficiency  ;  Diagram  of  maximum,  20. 
Engine  Equipped   with    Independent    Jet 

Condenser ;  Stopping  an,  35. 
Engine  equipped  with  Induction  Condenser; 

Stopping  and  starting  an,  51. 
Engine    equipped     with    Jet     Condenser; 

Starting  and  stopping  an,  33,  35. 
Evaporation ;  Condensing  by  means  of,  26. 

Feed-water  Temperature  when  Condens- 
ing ;  L,oss  in,  14. 
Flooding  due  to  Induction  Condenser  ;  Pre- 
vention of,  50. 

Head  and  Pressure  of  Water;  Relation 
between,  2. 
Heat.    Effect  of— upon  a  vacuum,  7. 
Heat  in  a  Pound  of  Steam,  54. 
Heat  Units  required  to  convert  Water  into 
Steam,  52-54. 

I  nduction  Condenser  ,  The,  47-51. 
Induction  Condenser  ,  Adjustment  of,  49. 
Induction  Condenser;  Arrangement  of,  48. 
Induction  Condenser ;  Prevention  of  flood- 
ing due  to,  50 


INDEX. 


79 


Induction  Condenser;  Stopping  and  start- 
ing an  engine  equipped  with  an,  51. 
Injection  Main  ;  Size  of,  67. 
Injection ;  Starting  a  balky,  34. 
Injection  Water  Supply,  44, 
Injector  Condenser ;  The,  24,  25  and  41-46. 
Injector  Condenser ;  Advantages  of,  45. 
Injector  Condenser  ;  Arrangement  of,  43. 
Injector  Condenser  ;  Diagram  of  42. 

V  et  Condenser  ;  The,  28-35. 

Jet  Condenser  ;  Arrangement  of,  29. 

Jet  Condenser;  Starting  and  stopping  an 
engine  equipped  with  an  indepen- 
dent, 35. 

Jet  Condensers  ;  Types  of,  30. 


K 


n  o  w  1  e  s     Horizontal     Double- Acting 
Pumps  ;  Table  of,  71. 


Lift  of  Water  by  Vacuum,  6-7. 
Ivaidlaw-Dunn-Gordon  Horizontal  Double- 
Acting  Pumps  ;  Table  of,  72. 


M 


I  easurement  of  Atmospheric  Pressure,  3. 
Measurement  of  a  Vacuum,  4-5. 
Motor-Driven  Pumps,  40. 


I^ressure  ;  Absolute,  9. 

Pressure  and  Temperature ;  Relations  be- 
tween, 8-9. 

Pressure  of  a  Column  of  Water,  2. 

Pressure  of  the  Atmosphere,  3. 

Pump  ;  Air.    See  Air-pump. 

Pump  Displacement  required  for  Water  to 
Condense,  57. 

Pump ;  Circulating,  39-40. 

Pump  Rating,  61. 

Pump  Suction,  6-7. 

Pump  Tables  ;  See  tables  of  pump  data. 

Pumps ;  Motor-driven,  40. 

Pumping  Air,  10. 

Pumping  Hot  Water,  7-8. 


f"l elief  Valves,  31. 

Starting  and  stopping  an  engine  equipped 
with  Induction  Condenser,  51. 

Starting  an  engine  equipped  with  a  Jet  Con- 
denser, 33. 

Steam  below  Atmospheric  Pressure  ;  Tem- 
perature of,  8. 

Steam  ;  Heat,  in  a  pound  of,  52. 

Steam ;  Heat  required  to  convert  water 
into,  52-54. 

Steam  ;  Physical  properties  of,  53. 

Steam ;  Water  required  to  condense,  15,  16 
and  55-57. 


Stopping  an  engine  equipped  with  a   Jet 

Condenser,  35. 
Surface  Condenser  ;  The,  23  and  36-40. 
Surface  Condenser  ;  Air-pump  for,  65. 
Surface  Condenser  ;  Area  of  cooling  surface 

in,  65-66. 
Surface  Condenser  ;  Details  of  the,  37-38. 
Surface  Condenser  ;  Sectional  view  of  a,  37. 
Snow    Horizontal    Double-Acting    Pumps ; 

Table  of,  73. 

I   ables  of  Pump  Data  : 

Barr  Horiz.  Double-Acting,  77. 
Conover  Vert.  Single-Acting,  69. 
Dean  Bros.,  Horiz.  Double-Acting,  70. 
Dean    Bros.    Twin    Cylinder  Vertical 

Single-Acting,  76. 
Deane  Horiz.  Double-Acting,  75. 
Knowles  Horiz.  Double-Acting,  7:. 
I,aidlaw-Dunn-Gordon  Horizontal 

Double-Acting,  72. 
Snow  Horiz.  Double-Acting,  73. 
Worthington    Horiz.    Double-Acting, 
74- 
Temperature   and    Pressure  ;   Relation  be- 
tween, 8-9. 
Temperature  and  Vacuum ;    Relation    be- 
tween, 68. 
Temperature  of  Feed- Water  when  Condens- 
ing, 14. 
Temperature  of  Steam  below  Atmospheric 

Pressure,  8. 
Tower ;  Cooling,  26. 

Vacuum  and  Temperature ;  Relation  be- 
tween, 68. 
Vacuum  Breakers.  31-32. 
Vacuum  ;  Effect  of  heat  upon  a,  7. 
Vacuum  ;  lifting  water  by  means  of  a,  6-7. 
Vacuum  ;  Measurement  of  a,  4-5. 
Vacuum  produced  by  Condensation,  ir. 
Valves ;  lifting  or  clattering  of  air-pump, 

27. 
Valves ;  Relief,  31. 

W  ater  Column  ;  Pressure  of  a,  2. 

Water  to  Condense  ;  Pump  displacement 
required  for,  57. 

Water ;  Feed.    See  Feed  water. 

Water  lifted  by  means  of  a  Vacuum,  6-7. 

Water  ;  Pumping  hot,  8. 

Water  required  per  Horsepower  for  Con- 
densing, in  gallons,  67. 

Water  required  to  Condense  Steam,  15-16 
and  55-57. 

Water  into  Steam ;  Heat  units  required  to 
convert,  52-54. 

Water  Supply  ;  Injection,  44. 

Worthington  Horizontal  Double-Acting 
Pumps ;  Table  of,  74. 


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Low,  F.R.  L9 

Condensers. 


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